Lipid Association-induced N- and C-terminal Domain Reorganization in Human Apolipoprotein E3

Apolipoprotein E (apoE) is a 299 amino acid, anti-atherogenic protein that plays a key role in regulating plasma lipoprotein metabolism. It is composed of an N-terminal (NT) domain (residues 1–191) that is responsible for binding to members of the low density lipoprotein receptor family and a C-terminal (CT) domain (residues 216–299) that anchors the protein to lipoprotein particles by virtue of its high-affinity lipid binding characteristics. Isoform-specific differences in the NT domain that modulate the lipoprotein binding preference elicited by the CT domain suggest the existence and importance of domain interactions in this protein. Employing steady state fluorescence quenching and resonance energy transfer techniques, spatial proximity relationships between the N- and C-terminal domains were investigated in recombinant human apoE3. ApoE3 containing a single Trp at position 264 and anN-iodoacetyl-N′-(5-sulfo-1-napthyl) ethylenediamine (AEDANS) moiety covalently attached to the lone Cys residue at position 112 was used (AEDANS-apoE3/[email protected]). Fluorescence quenching studies revealed a solvent-exposed location for Trp-264. In the lipid-free state, fluorescence resonance energy transfer (FRET) was noted between Trp-264 and AEDANS, with a calculated distance of 27 Å between the two fluorophores. Control experiments established that FRET observed in this system is intramolecular. FRET was abolished upon proteolysis in the linker region connecting the NT and CT domains. Lowering the solution pH to 4 induced an increase in the efficiency of intramolecular energy transfer, with the two domains reorienting about 5 Å closer to one another. Interdomain FRET was retained in the presence of 0.6–1.0 m guanidine hydrochloride but was lost at higher concentrations, a manifestation of unfolding of the domains and increased distance between the donor-acceptor pair. Interaction of AEDANS-apoE3/[email protected] with lipid induced a loss of FRET, attributed to spatial repositioning of the domains by >80 Å. The data provide biophysical evidence that, in addition to reported conformational changes in the four-helix bundle configuration induced by lipid association, lipid binding of apoE is accompanied by reorientation of the tertiary disposition of the NT and CT domains. Apolipoprotein E (apoE) is a 299 amino acid, anti-atherogenic protein that plays a key role in regulating plasma lipoprotein metabolism. It is composed of an N-terminal (NT) domain (residues 1–191) that is responsible for binding to members of the low density lipoprotein receptor family and a C-terminal (CT) domain (residues 216–299) that anchors the protein to lipoprotein particles by virtue of its high-affinity lipid binding characteristics. Isoform-specific differences in the NT domain that modulate the lipoprotein binding preference elicited by the CT domain suggest the existence and importance of domain interactions in this protein. Employing steady state fluorescence quenching and resonance energy transfer techniques, spatial proximity relationships between the N- and C-terminal domains were investigated in recombinant human apoE3. ApoE3 containing a single Trp at position 264 and anN-iodoacetyl-N′-(5-sulfo-1-napthyl) ethylenediamine (AEDANS) moiety covalently attached to the lone Cys residue at position 112 was used (AEDANS-apoE3/[email protected]). Fluorescence quenching studies revealed a solvent-exposed location for Trp-264. In the lipid-free state, fluorescence resonance energy transfer (FRET) was noted between Trp-264 and AEDANS, with a calculated distance of 27 Å between the two fluorophores. Control experiments established that FRET observed in this system is intramolecular. FRET was abolished upon proteolysis in the linker region connecting the NT and CT domains. Lowering the solution pH to 4 induced an increase in the efficiency of intramolecular energy transfer, with the two domains reorienting about 5 Å closer to one another. Interdomain FRET was retained in the presence of 0.6–1.0 m guanidine hydrochloride but was lost at higher concentrations, a manifestation of unfolding of the domains and increased distance between the donor-acceptor pair. Interaction of AEDANS-apoE3/[email protected] with lipid induced a loss of FRET, attributed to spatial repositioning of the domains by >80 Å. The data provide biophysical evidence that, in addition to reported conformational changes in the four-helix bundle configuration induced by lipid association, lipid binding of apoE is accompanied by reorientation of the tertiary disposition of the NT and CT domains. apolipoprotein E N-iodoacetyl-N′-(5-sulfo-1-napthyl) ethylenediamine C-terminal dimyristoylphosphatidylcholine fluorescence resonance energy transfer guanidine hydrochloride lysophosphatidylcholine N-terminal high performance liquid chromatography Apolipoprotein E (apoE),1 a resident of several classes of plasma lipoprotein, plays a key role in regulating plasma cholesterol and triglyceride homeostasis (1Weisgraber K.H. Adv. Prot. Chem. 1994; 45: 249-302Crossref PubMed Google Scholar, 2Mahley R.W. Science. 1988; 240: 622-630Crossref PubMed Scopus (3377) Google Scholar) by virtue of its ability to act as a ligand for the low density lipoprotein (LDL) family of receptors (3Brown M.S. Goldstein J.L. Science. 1986; 232: 34-47Crossref PubMed Scopus (4350) Google Scholar). Transgenic mice overexpressing apoE manifest decreased cholesterol levels on chow diet and a marked resistance to diet-induced hypercholesterolemia (4Shimano H. Yamada N. Katsuki M. Yamamoto K. Gotoda T. Harada K. Shimada M. Yazaki T. J. Clin. Invest. 1992; 90: 2084-2091Crossref PubMed Scopus (82) Google Scholar), while apoE knockout mice exhibit massive accumulation of remnant lipoproteins (5Zhang S.H. Reddick R.L Piedrahita J.A. Maeda N. Science. 1992; 258: 468-471Crossref PubMed Scopus (1836) Google Scholar). These studies emphasize its principal role in lipoprotein metabolism, while other studies suggest an emerging role for apoE in nerve regeneration and Alzheimer's disease (2Mahley R.W. Science. 1988; 240: 622-630Crossref PubMed Scopus (3377) Google Scholar). Studies of apoE structure-function relationship identified two independently folded domains in the protein (6Wetterau J.R. Aggerbeck L.P. Rall Jr., S.C. Weisgraber K.H. J. Biol. Chem. 1988; 263: 6240-6248Abstract Full Text PDF PubMed Google Scholar, 7Aggerbeck L.P. Wetterau J.R. Weisgraber K.H. Wu C-S.C. Lindgren F.T. J. Biol. Chem. 1988; 263: 6249-6258Abstract Full Text PDF PubMed Google Scholar). The 34-kDa, 299-residue protein is composed of a 22-kDa N-terminal (NT) domain (residues 1–191) linked to a 10-kDa C-terminal (CT) domain (residues 216–299) via a protease-sensitive loop localized between residues 191 and 216 (see Fig. 1). The NT domain houses the LDL receptor binding region and bears weak lipid binding capability (1Weisgraber K.H. Adv. Prot. Chem. 1994; 45: 249-302Crossref PubMed Google Scholar), while the CT domain accommodates high affinity lipid binding sites (6Wetterau J.R. Aggerbeck L.P. Rall Jr., S.C. Weisgraber K.H. J. Biol. Chem. 1988; 263: 6240-6248Abstract Full Text PDF PubMed Google Scholar, 7Aggerbeck L.P. Wetterau J.R. Weisgraber K.H. Wu C-S.C. Lindgren F.T. J. Biol. Chem. 1988; 263: 6249-6258Abstract Full Text PDF PubMed Google Scholar, 8Yokoyama S. Kawai Y. Tajima S. Yamamoto A. J. Biol. Chem. 1985; 260: 16375-16382Abstract Full Text PDF PubMed Google Scholar). X-ray crystal analysis of the isolated NT domain of apoE (9Wilson C. Wardell M.R. Weisgraber K.H. Mahley R.W. Agard D.A. Science. 1991; 252: 817-822PubMed Google Scholar) reveals four amphipathic α-helices that sequester their hydrophobic faces to form a helix-bundle in the lipid-free state. Our knowledge of the molecular architecture and structural hierarchy of the CT domain of apoE is limited, though selected peptide segments have been crystallized (10Forstner M. Peters-Libeu C. Contreras-Forrest E. Newhouse Y. Knapp M. Rupp B. Weisgraber K.H. Protein Expr. Purif. 1999; 17: 267-272Crossref PubMed Scopus (27) Google Scholar). Secondary structure algorithms identify a high degree of α-helicity in the CT domain, with three segments bearing potential amphipathic α-helical propensities (11Segrest J.-P. Jones M.K. DeLoof H. Brouillette C.G Venkatachalapathi M. Anantharamaiah G.M. J. Lipid Res. 1992; 33: 141-166Abstract Full Text PDF PubMed Google Scholar, 12De Pauw M. Vanloo B. Dergunov A.D. Devreese A.-M. J. M. Google Scholar). studies that the CT domain is responsible for of apoE L.P. Wetterau J.R. Weisgraber K.H. Wu C-S.C. Lindgren F.T. J. Biol. Chem. 1988; 263: 6249-6258Abstract Full Text PDF PubMed Google Scholar, 8Yokoyama S. Kawai Y. Tajima S. Yamamoto A. J. Biol. Chem. 1985; 260: 16375-16382Abstract Full Text PDF PubMed Google Scholar, J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar), an by C-terminal was to J.A. Weisgraber K.H. J. Biol. Chem. Full Text PDF PubMed Google Scholar). this that binding to low density lipoprotein this of the CT domain as an lipoprotein binding in The NT and CT domains have been to of their in In the state, the isolated NT domain Rall Jr., S.C. Weisgraber K.H. Mahley R.W. J. Biol. Chem. 258: Full Text PDF PubMed Google Scholar), while the CT been to capability D.A. M. Jr., 1992; PubMed Scopus Google Scholar, Pauw M. Vanloo B. Weisgraber K.H. M. PubMed Scopus Google Scholar). in the NT domain have on the lipoprotein binding preference of by the CT The by amino at 112 and and Cys and at while the a Cys at 112 and at (1Weisgraber K.H. Adv. Prot. Chem. 1994; 45: 249-302Crossref PubMed Google Scholar). a preference for binding to C. Wardell M.R. T. Mahley R.W. Weisgraber K.H. Agard D.A. J. Biol. Chem. 1994; Full Text PDF PubMed Google Scholar, Weisgraber K.H. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar), while and with high density lipoproteins (1Weisgraber K.H. Adv. Prot. Chem. 1994; 45: 249-302Crossref PubMed Google Scholar). In the protein the structural of the two domains with to other is The of a in the NT domain and in the CT the binding preference of for C. Wardell M.R. T. Mahley R.W. Weisgraber K.H. Agard D.A. J. Biol. Chem. 1994; Full Text PDF PubMed Google Scholar, Weisgraber K.H. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar) the of domain is in the in the between apoE and by the CT domain Weisgraber K.H. M. A.D. S. A. 90: PubMed Scopus Google Scholar). J.A. S. Knapp M. Rupp B. Weisgraber K.H. PubMed Scopus Google Scholar) observed that the NT domain the differences in the apoE the that apoE receptor binding ability E. Y. J. Biol. Chem. Full Text PDF PubMed Google Scholar) to the that the CT domain anchors the protein to the lipid while the NT domain conformational changes that modulate receptor binding PubMed Scopus Google Scholar). lipid binding the capability of is to the structural disposition of apoE domains in solution and that upon lipid was that lipid binding structural changes in isolated NT of the of the bundle J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, B. J.A. Weisgraber K.H. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). In the have used a of and steady state fluorescence to spatial relationships between the NT and CT domains in in and was the containing a single residue at position 112 in the NT domain was used the In one of the but one of the Trp residues in were to a protein with a single Trp in the CT the were to was was to the presence of the and the of human were in E. the system The is in the of a with was by affinity chromatography by by as J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar), a of revealed that the the structural of the protein. experiments of protected] and in that the as and higher state as reported by L.P. Wetterau J.R. Weisgraber K.H. Wu C-S.C. Lindgren F.T. J. Biol. Chem. 1988; 263: 6249-6258Abstract Full Text PDF PubMed Google Scholar, 8Yokoyama S. Kawai Y. Tajima S. Yamamoto A. J. Biol. Chem. 1985; 260: 16375-16382Abstract Full Text PDF PubMed Google Scholar, J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). of ethylenediamine (AEDANS) was as J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). The was as the at for AEDANS, for protected] and for at Fluorescence were on a for and were an of to were in pH at of was The density of the was to the of protected] AEDANS-apoE3/[email protected] were with of to Fluorescence were at for Trp and for The quenching were on the and the fluorescence in the and presence of and is the of the The of the of is the quenching J.R. of Fluorescence Google Scholar). Fluorescence quenching of was with and with in a the 4 Trp residues were by and was to was The protein was as J. Biol. PubMed Scopus Google Scholar). The efficiency of energy transfer in AEDANS-apoE3/[email protected] was calculated on in fluorescence PubMed Scopus Google Scholar), and is by and the of the in the and presence of (AEDANS-apoE3/[email were calculated on a of for in J. PubMed Scopus Google Scholar). The distance of between the energy and is calculated as in the T. Scholar), is the distance at the transfer efficiency is is is the of the and of for used PubMed Scopus Google Scholar) on of the is the of the to J.R. of Fluorescence Google Scholar), and is the calculated as J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). FRET was fluorescence with at fluorescence of at was the of FRET, of protected] and AEDANS-apoE3/[email protected] and were at 4 and fluorescence of the were at proteolysis of AEDANS-apoE3/[email protected] was as by Wetterau (6Wetterau J.R. Aggerbeck L.P. Rall Jr., S.C. Weisgraber K.H. J. Biol. Chem. 1988; 263: 6240-6248Abstract Full Text PDF PubMed Google Scholar). The protein was with at a in pH at for In studies the of pH on FRET, fluorescence were on AEDANS-apoE3/[email protected] and in the pH m pH m pH 4 were for fluorescence of at at the the of on FRET, AEDANS-apoE3/[email protected] were with and m in m pH for at The lipid state of protein was in two state state, FRET was in the presence of lysophosphatidylcholine and was protected] in the FRET were with the protected] and protected] and and protected] and were by of protein with at for were by The were protein and by density as J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). Trp at and in the NT domain, 264 and in the CT domain, and position in the loop the NT and CT domains. of were to a single Trp at position 264 as a in the CT In Trp-264 at the of a amphipathic residues (11Segrest J.-P. Jones M.K. DeLoof H. Brouillette C.G Venkatachalapathi M. Anantharamaiah G.M. J. Lipid Res. 1992; 33: 141-166Abstract Full Text PDF PubMed Google Scholar). fluorescence of Trp-264 was to its in of its location in the of in an of protected] at a with at a location of Trp-264. and Trp-264 fluorescence quenching of and In Trp was to the and a of with reported by M.R. PubMed Scopus Google Scholar). an apoE the lone is in a reported was The was and for and quenching for this protein were a location of structure analysis (9Wilson C. Wardell M.R. Weisgraber K.H. Mahley R.W. Agard D.A. Science. 1991; 252: 817-822PubMed Google Scholar) that residue is in the protein fluorescence quenching the fluorescence data that Trp-264 an location in the CT and quenching of apoE three three in a The single Cys at position 112 on in the NT domain of protected] was covalently with the The of the protein were to of apoE3. The of quenching fluorescence by and were and The crystal structure that is in a location in the It is that the moiety a location as between Trp-264 and a donor-acceptor J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, M. J. Biol. PubMed Scopus Google Scholar, J. M. M. M. J. Biol. Chem. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar) to spatial proximity and distance relationships between the NT and CT domains of by FRET 1). fluorescence of protected] and AEDANS-apoE3/[email protected] in the lipid-free state at protected] a attributed to of the single Trp at position In the of AEDANS-apoE3/[email a in at was with the of a fluorescence at a at is to fluorescence energy transfer Trp-264. for the of fluorescence of AEDANS, a Trp was Fluorescence of was the fluorescence at in AEDANS-apoE3/[email protected] is the of the of at been of protein. ApoE3 in J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). of apoE S. Kawai Y. Tajima S. Yamamoto A. J. Biol. Chem. 1985; 260: 16375-16382Abstract Full Text PDF PubMed Google Scholar) is to by a amphipathic residues in the CT domain J.A. Weisgraber K.H. J. Biol. Chem. Full Text PDF PubMed Google Scholar). this the potential of FRET to the in Fig. was three In the FRET was in the is on one while the on an FRET was observed protected] was in a with as by of of fluorescence at changes in Trp fluorescence at FRET was observed of the for to at 4 In a FRET was in AEDANS-apoE3/[email protected] with that in on AEDANS-apoE3/[email protected] by that the the in FRET was noted that the of FRET in lipid-free apoE is FRET was as a of of AEDANS-apoE3/[email protected] in to about transfer is a in efficiency upon of the the is a state. was in the of fluorescence between and between and AEDANS-apoE3/[email that is in the distance between the two fluorophores. concentrations, a increase in FRET was noted The of fluorescence at of AEDANS-apoE3/[email protected] analysis revealed a in the a and state the data that FRET in lipid-free AEDANS-apoE3/[email protected] is intramolecular. the energy transfer in the at transfer efficiency is between the and in lipid-free AEDANS-apoE3/[email protected] was calculated to Å. on this a distance of of Å was calculated between Trp-264 and and between donor-acceptor in lipid-free and of and three of FRET analysis of and three of FRET analysis in a the intramolecular of FRET between the NT and CT domains in investigated the of at the linker between the domains on the efficiency of energy studies reported that of apoE in the of NT and CT (6Wetterau J.R. Aggerbeck L.P. Rall Jr., S.C. Weisgraber K.H. J. Biol. Chem. 1988; 263: 6240-6248Abstract Full Text PDF PubMed Google Scholar). fluorescence of AEDANS-apoE3/[email protected] and transfer was lost upon as by the of fluorescence at was a in Trp fluorescence of increased of Trp-264 FRET was in AEDANS-apoE3/[email protected] as a of solution pH in Trp fluorescence with a increase in was noted as a of with fluorescence observed at pH The Trp in AEDANS-apoE3/[email protected] at pH 4 the quenching to increased to increased FRET as a of the to the The was by the fluorescence of protected] as a of pH In this was a in Trp fluorescence that energy transfer is the responsible for the observed in Trp of protected] and at pH was that the observed FRET was intramolecular on energy transfer at pH 4 the distance between Trp-264 and on was calculated to about 5 Å closer the distance at pH The of to in protein structural was used as a to domain in lipid-free apoE3. The of to a in the structure of the CT and NT domains and (6Wetterau J.R. Aggerbeck L.P. Rall Jr., S.C. Weisgraber K.H. J. Biol. Chem. 1988; 263: 6240-6248Abstract Full Text PDF PubMed Google Scholar, 7Aggerbeck L.P. Wetterau J.R. Weisgraber K.H. Wu C-S.C. Lindgren F.T. J. Biol. Chem. 1988; 263: 6249-6258Abstract Full Text PDF PubMed Google Scholar, 12De Pauw M. Vanloo B. Dergunov A.D. Devreese A.-M. J. M. Google Scholar). FRET was in AEDANS-apoE3/[email protected] as a of to m changes in FRET were as by the in Trp-264 and fluorescence m and a in Trp-264 was while at and was a in of protected] were as a of was in Trp-264 fluorescence was observed at m to in the of Trp-264. The of at and is as a of changes in FRET between the domains with loss of FRET at higher The of binding AEDANS-apoE3/[email protected] to lipid on FRET was in two and binding to lysophosphatidylcholine a loss in energy transfer was as by a in fluorescence to for the observed in Trp fluorescence of protected] in the presence of was at in Trp was accompanied by a in of fluorescence that the of Trp-264 is with the to an as the on the The loss in energy transfer a structural of the two domains was noted in the of FRET were calculated for the donor-acceptor in the presence of a Å in the of The distance of between Trp-264 and in the state was calculated as FRET was of a distance of of >80 Å between the donor-acceptor pair. FRET were with protected] as with marked in FRET as by the in the observed fluorescence intramolecular FRET, were with AEDANS-apoE3/[email protected] with an energy transfer was in this of intramolecular FRET in the form of AEDANS-apoE3/[email protected] with protected] and were to FRET was a of fluorescence was noted at as a of FRET Trp-264 on one to on a on a an of remnant lipoprotein is of in conformational and at 112 and in the NT domain of apoE manifest differences in The two independently folded and structural domains in apoE by and biophysical (6Wetterau J.R. Aggerbeck L.P. Rall Jr., S.C. Weisgraber K.H. J. Biol. Chem. 1988; 263: 6240-6248Abstract Full Text PDF PubMed Google Scholar, 7Aggerbeck L.P. Wetterau J.R. Weisgraber K.H. Wu C-S.C. Lindgren F.T. J. Biol. Chem. 1988; 263: 6249-6258Abstract Full Text PDF PubMed Google Scholar, J.A. S. Knapp M. Rupp B. Weisgraber K.H. PubMed Scopus Google Scholar). this in the NT domain been to the lipoprotein binding preference of the CT domain in the C. Wardell M.R. T. Mahley R.W. Weisgraber K.H. Agard D.A. J. Biol. Chem. 1994; Full Text PDF PubMed Google Scholar, Weisgraber K.H. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar) and the binding interactions of apoE with the peptide Weisgraber K.H. M. A.D. S. A. 90: PubMed Scopus Google Scholar). domain interactions in apoE have in a as a for and Alzheimer's disease analysis of apoE that residues and in the CT domain have the to form amphipathic α-helices (9Wilson C. Wardell M.R. Weisgraber K.H. Mahley R.W. Agard D.A. Science. 1991; 252: 817-822PubMed Google Scholar), with the two segments to other Pauw M. Vanloo B. Dergunov A.D. Devreese A.-M. J. M. Google Scholar). of a amphipathic on the of and on the with The (residues bears of a is to (11Segrest J.-P. Jones M.K. DeLoof H. Brouillette C.G Venkatachalapathi M. Anantharamaiah G.M. J. Lipid Res. 1992; 33: 141-166Abstract Full Text PDF PubMed Google Scholar), but a hydrophobic that residues were to sites of as analysis of CT J.A. Weisgraber K.H. J. Biol. Chem. Full Text PDF PubMed Google Scholar). on this analysis and fluorescence data and high for Trp-264 to in with sites on a apoE but in a solvent-exposed as the on a a location is a of residues Trp-264 at the The of FRET in lipid-free AEDANS-apoE3/[email protected] is a of spatial proximity between the NT and CT domains. the of apoE to a was to the of FRET in this with that FRET in protected] is intramolecular in The distance of 27 Å that the two domains in a with to at selected sites by tertiary and and by the that between residues 191 and in of the and as by loss of of the two domains by proteolysis to of Trp-264 fluorescence to the observed in the protein in the of that proteolysis in increased of this was that the NT and CT domains in L.P. Wetterau J.R. Weisgraber K.H. Wu C-S.C. Lindgren F.T. J. Biol. Chem. 1988; 263: 6249-6258Abstract Full Text PDF PubMed Google Scholar) and J.A. S. Knapp M. Rupp B. Weisgraber K.H. PubMed Scopus Google Scholar) an accumulation of the CT domain as a was that the the protein in a configuration the tertiary interactions between NT and CT domains in the lipid-free state. the that weak interactions the two domains in lipid-free pH and to in protein in efficiency of energy transfer were noted upon the with the at pH of the two domains the structure been to retained in at pH 4 J. Biol. PubMed Scopus Google Scholar), the of pH on the structural of the CT domain is It is that of the domains to In other isolated NT was that the solution pH increased binding of acid, a hydrophobic that to hydrophobic A. C. Aggerbeck L.P. J. 1999; PubMed Scopus Google Scholar, J. PubMed Scopus Google Scholar). in the CT domain as and is that hydrophobic interactions the two domains closer to other at pH that apoE a of with with the of for the between and while that for the at m (6Wetterau J.R. Aggerbeck L.P. Rall Jr., S.C. Weisgraber K.H. J. Biol. Chem. 1988; 263: 6240-6248Abstract Full Text PDF PubMed Google Scholar, 7Aggerbeck L.P. Wetterau J.R. Weisgraber K.H. Wu C-S.C. Lindgren F.T. J. Biol. Chem. 1988; 263: 6249-6258Abstract Full Text PDF PubMed Google Scholar, 12De Pauw M. Vanloo B. Dergunov A.D. Devreese A.-M. J. M. Google Scholar). The two to unfolding of the CT and NT domains of on and biophysical studies (6Wetterau J.R. Aggerbeck L.P. Rall Jr., S.C. Weisgraber K.H. J. Biol. Chem. 1988; 263: 6240-6248Abstract Full Text PDF PubMed Google Scholar, A. Biol. Chem. 1992; PubMed Scopus Google Scholar), was that of apoE and unfolding of CT domain in the between and low to of the structure is to on analysis (6Wetterau J.R. Aggerbeck L.P. Rall Jr., S.C. Weisgraber K.H. J. Biol. Chem. 1988; 263: 6240-6248Abstract Full Text PDF PubMed Google Scholar, J.A. S. Knapp M. Rupp B. Weisgraber K.H. PubMed Scopus Google Scholar). FRET analysis that the between the two domains is to FRET was with unfolding of the at the CT domain by the NT domain at higher The in Trp-264 observed at m in protected] and AEDANS-apoE3/[email protected] structural in the of to of this The in observed at and m loss of FRET as a of structural of the four-helix bundle NT domain and the two as the protein Trp-264 is in the of the CT domain and as a for lipid in the of the two domains. to lipid as to energy transfer between Trp-264 and a in the disposition of the NT and CT domains. the of FRET is to the of that the distance of between the and is >80 Å on a lipid It is that apoE is as a in the state, with the two domains other but linked at the loop a is lipid-free apoE is to upon lipid binding S. Kawai Y. Tajima S. Yamamoto A. J. Biol. Chem. 1985; 260: 16375-16382Abstract Full Text PDF PubMed Google Scholar, S. PubMed Scopus Google Scholar). In the of a induced of and J. Lipid Res. 1999; Full Text Full Text PDF PubMed Google Scholar). In the presence of the bundle was to an about a region B. J.A. Weisgraber K.H. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar), by an of 4 to a J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). studies this evidence of domain upon with a lipid that the for this the of segments to with the lipid tertiary in the lipid-free state. studies of apoE in the presence of a PubMed Scopus Google Scholar), with a of hydrophobic residues and to binding of apoE to lipid In the that of protected] with in a in Trp that Trp-264 and its in the protein to the in the state, with quenching of fluorescence by the biophysical evidence of spatial proximity between the NT and CT domains in that is upon lipid lipid-free apoE receptor binding is that the CT domain the NT domain in a lipid the CT domain its higher lipid by domain repositioning and binding of the NT domain, that is to by other to proximity relationships between segments of apoE domains in solution and in lipoprotein the and of the domains in the molecular of of as as of lipoprotein particles and its role in and and for and

Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.