Cooperativity between the Hydrophobic and Cross-linking Domains of Elastin

The principal protein component of the elastic fiber found in elastic tissues is elastin, an amorphous, cross-linked biopolymer that is assembled from a high molecular weight monomer. The hydrophobic and cross-linking domains of elastin have been considered separate and independent, such that changes to one region are not thought to affect the other. However, results from these solid-state 13C NMR experiments demonstrate that cooperativity in protein folding exists between the two domain types. The sequence of the EP20-24-24 polypeptide has three hydrophobic sequences from exons 20 and 24 of the soluble monomer tropoelastin, interspersed with cross-linking domains constructed from exons 21 and 23. In the middle of each cross-linking domain is a “hinge” sequence. When this pentapeptide is replaced with alanines, as in EP20-24-24[23U], its properties are changed. In addition to the expected increase in α-helical content and the resulting increase in rigidity of the cross-linking domains, changes to the organization of the hydrophobic regions are also observed. Using one-dimensional CPMAS (cross-polarization with magic angle spinning) techniques, including spectral editing and relaxation measurements, evidence for a change in dynamics to both domain types is observed. Furthermore, it is likely that the methyl groups of the leucines of the hydrophobic domains are also affected by the substitution to the hinge region of the cross-linking sequences. This cooperativity between the two domain types brings new questions to the phenomenon of coacervation in elastin polypeptides and strongly suggests that functional models for the protein must include a role for the cross-linking regions. The principal protein component of the elastic fiber found in elastic tissues is elastin, an amorphous, cross-linked biopolymer that is assembled from a high molecular weight monomer. The hydrophobic and cross-linking domains of elastin have been considered separate and independent, such that changes to one region are not thought to affect the other. However, results from these solid-state 13C NMR experiments demonstrate that cooperativity in protein folding exists between the two domain types. The sequence of the EP20-24-24 polypeptide has three hydrophobic sequences from exons 20 and 24 of the soluble monomer tropoelastin, interspersed with cross-linking domains constructed from exons 21 and 23. In the middle of each cross-linking domain is a “hinge” sequence. When this pentapeptide is replaced with alanines, as in EP20-24-24[23U], its properties are changed. In addition to the expected increase in α-helical content and the resulting increase in rigidity of the cross-linking domains, changes to the organization of the hydrophobic regions are also observed. Using one-dimensional CPMAS (cross-polarization with magic angle spinning) techniques, including spectral editing and relaxation measurements, evidence for a change in dynamics to both domain types is observed. Furthermore, it is likely that the methyl groups of the leucines of the hydrophobic domains are also affected by the substitution to the hinge region of the cross-linking sequences. This cooperativity between the two domain types brings new questions to the phenomenon of coacervation in elastin polypeptides and strongly suggests that functional models for the protein must include a role for the cross-linking regions. Elasticity in blood vessels and skin originates from elastin, an insoluble and amorphous protein assembled from its soluble monomer tropoelastin (1Debelle L. Tamburro A.M. Int. J. Biochem. Cell Biol. 1999; 31: 261-272Crossref PubMed Scopus (384) Google Scholar, 2Rosenbloom J. Abrams W.R. Mecham R. FASEB J. 1993; 7: 1208-1218Crossref PubMed Scopus (506) Google Scholar, 3Sandberg L.B. Int. Rev. Connective Tissue Res. 1976; 7: 160-207Google Scholar). Tropoelastin and insoluble elastin are typically described as having two types of domains, cross-linking and hydrophobic. The former are usually polyalanine regions, typically found as KAAK or KAAAK motifs, whereas the latter are dominated by polypenta- or polyhexapeptide repeats. Because the molecular weight of tropoelastin is typically large (>70 kDa) and its composition complex, significant effort has been placed into identifying and characterizing elastin peptides (4Urry D.W. Adv. Exp. Med. Biol. 1974; 43: 211-243Crossref PubMed Scopus (55) Google Scholar, 5Urry D.W. Long M.M. Adv. Exp. Med. Biol. 1977; 79: 685-714Crossref PubMed Scopus (55) Google Scholar, 6Venkatachalam C.M. Urry D.W. Macromolecules. 1981; 14: 1225-1229Crossref Scopus (128) Google Scholar, 7Chang D.K. Venkatachalam C.M. Prasad K.U. Urry D.W. J. Biomol. Struct. Dynam. 1989; 6: 851-858Crossref PubMed Scopus (37) Google Scholar, 8Luan C.-H. Krishna N.R. Urry D.W. Intl. J. Quantum Chem. Symp. 1990; 18: 183-198Google Scholar, 9Tamburro A.M. Guantieri V. Gordini D.D. J. Biomol. Struct. Dyn. 1992; 10: 441-454Crossref PubMed Scopus (54) Google Scholar, 10Martino M. Coviello A. Tamburro A.M. Int. J. Biol. Macromol. 2000; 27: 59-64Crossref PubMed Scopus (46) Google Scholar, 11Martino M. Tamburro A.M. Biopolymers. 2001; 59: 29-37Crossref PubMed Scopus (44) Google Scholar). These mimetics range from the simple repeating polypeptides based on the VPGVG subunit, to those that more closely mirror the more complex native sequence. In particular, Keeley and coworkers (12Bellingham C.M. Woodhouse K.A. Robson P. Rothstein S.J. Keeley F.W. Biochim. Biophys. Acta. 2001; 1550: 6-19Crossref PubMed Scopus (135) Google Scholar, 13Miao M. Bellingham C.M. Stahl R.J. Sitarz E.E. Lane C.J. Keeley F.W. J. Biol. Chem. 2003; 276: 48553-48562Abstract Full Text Full Text PDF Scopus (146) Google Scholar, 14Miao M. Cirulis J.T. Lee S. Keeley F.W. Biochemistry. 2005; 44: 14367-14375Crossref PubMed Scopus (89) Google Scholar) have recently reported a series of related polypeptides that are composed of alternating hydrophobic and cross-linking domains. These polypeptides have been shown to mimic various characteristics of the native protein, including coacervation and elasticity (12Bellingham C.M. Woodhouse K.A. Robson P. Rothstein S.J. Keeley F.W. Biochim. Biophys. Acta. 2001; 1550: 6-19Crossref PubMed Scopus (135) Google Scholar, 13Miao M. Bellingham C.M. Stahl R.J. Sitarz E.E. Lane C.J. Keeley F.W. J. Biol. Chem. 2003; 276: 48553-48562Abstract Full Text Full Text PDF Scopus (146) Google Scholar, 14Miao M. Cirulis J.T. Lee S. Keeley F.W. Biochemistry. 2005; 44: 14367-14375Crossref PubMed Scopus (89) Google Scholar, 15Bellingham C.M. Lillie M.A. Gosline J.M. Wright G.M. Starcher B.C. Bailey A.J. Woodhouse K.A. Keeley F.W. Biopolymers. 2003; 70: 445-455Crossref PubMed Scopus (219) Google Scholar). Many structural questions may be addressed with these mimetics. For instance, does a change in the sequence of one domain type impact the other? Which modifications impact the overall protein structure? Moreover, how can these structural changes be used to identify key features of the functional models of the proteins? For this study, two related elastin-like polypeptides were synthesized. EP20-24-24 3The abbreviations used are: EP20-24-24, elastin peptide with the sequence encoded by exons 20-21/23-24-21/23-24; EP20-24-24[23U], the unhinged elastin polypeptide; CP, cross-polarization; CPD, cross-polarization with depolarization; CPMAS, cross-polarization with magic angle spinning. has five domains, constructed from exons 20 and 24 for the hydrophobic, and 21/23 for the cross-linking, as follows: Ex 20, FPGFGVGVGGIPGVAGVPGVGGVPGVGGVPGVGIS; Ex 21/23, PEAQAAAAAKAAKYGVGTPAAAAAKAAAKAAQF; Ex 24, GLVPGVGVAPGVGVAPGVGVAPGVGLAPGVGVAPGVGVAPGVGVAPAIG; Ex 21/23, PEAQAAAAAKAAKYGVGTPAAAAAKAAAKAAQF; and Ex 24, GLVPGVGVAPGVGVAPGVGVAPGVGLAPGVGVAPGVGVAPGVGVAPAIG. Because both tropoelastin and mature elastin typically have long multidomain sequences of alternating hydrophobic and cross-linking domains very similar to EP20-24-24, this polypeptide (and longer ones, such as EP20-244) is a reasonable mimic. Experiments by Keeley and coworkers, again, show that many of the physical properties of these polypeptides closely mirror those of the native protein (12Bellingham C.M. Woodhouse K.A. Robson P. Rothstein S.J. Keeley F.W. Biochim. Biophys. Acta. 2001; 1550: 6-19Crossref PubMed Scopus (135) Google Scholar, 13Miao M. Bellingham C.M. Stahl R.J. Sitarz E.E. Lane C.J. Keeley F.W. J. Biol. Chem. 2003; 276: 48553-48562Abstract Full Text Full Text PDF Scopus (146) Google Scholar, 14Miao M. Cirulis J.T. Lee S. Keeley F.W. Biochemistry. 2005; 44: 14367-14375Crossref PubMed Scopus (89) Google Scholar, 15Bellingham C.M. Lillie M.A. Gosline J.M. Wright G.M. Starcher B.C. Bailey A.J. Woodhouse K.A. Keeley F.W. Biopolymers. 2003; 70: 445-455Crossref PubMed Scopus (219) Google Scholar). Another polypeptide was synthesized to be identical to EP20-24-24, except the central pentapeptidyl turn, or “hinge” (underlined in the above representation), in each of the cross-linking domains has been substituted by alanines. Hence, it is called the “unhinged” elastin polypeptide EP20-24-24[23U]: Ex 20, FPGFGVGVGGIPGVAGVPGVGGVPGVGGVPGVGIS; Ex 21/23, PEAQAAAAAKAAKYAAAAAAAAAAKAAAKAAQF; Ex 24, GLVPGVGVAPGVGVAPGVGVAPGVGLAPGVGVAPGVGVAPGVGVAPAIG; Ex 21/23, PEAQAAAAAKAAKYAAAAAAAAAAKAAAKAAQF; and Ex 24, GLVPGVGVAPGVGVAPGVGVAPGVGLAPGVGVAPGVGVAPGVGVAPAIG. Table 1 illustrates the amino acid composition of EP20-24-24 and EP20-24-24[23U]. In addition to the obvious sequence similarities, the makeup of EP20-24-24 and EP20-24-24[23U] greatly resembles that of native elastin, with its predominance of the four small, hydrophobic amino acids: glycine, valine, proline, and alanine. Keeley and coworkers (14Miao M. Cirulis J.T. Lee S. Keeley F.W. Biochemistry. 2005; 44: 14367-14375Crossref PubMed Scopus (89) Google Scholar) have provided extensive evidence for changes in structure upon substitution of the hinge region by the five alanines. An increase in α-helical content from 8.5% in EP20-24-24 to 32.8% in EP20-24-24[23U] was determined by circular dichroism. In addition, the SDS-PAGE results of analogous hinged and unhinged elastin polypeptides show that the apparent molecular weight of the latter is higher, which is expected for a more rigid and rod-like structure. The SDS-PAGE results also indicate that the peptides are well behaved monomers. Finally, another reported result included the coacervation temperature of the unhinged polypeptide (12.5 °C), which is significantly lower than that observed for EP20-24-24 (29.0 °C).TABLE 1Amino acid composition of EP20-24-24 and EP20-24-24[23U]Hydrophobic regionCross-linking region, Exon 21/23Percent compositionNo. of methyl groupsAmino acidExon 20Exon 2420-24-24[23U]20-24-24[23U]20-24-24[23U]20-24-24[23U]20-24-24aLists numbers of methyl groups for each residue type.[23U]aLists numbers of methyl groups for each residue type.Ala111616263621.426.44353Gln0000442200Glu0000221100Gly151532328427.425.400Ile2222002288Leu0044002288Lys0000884400Phe2200222200Pro5518186414.413.400Ser1100000.50.500Thr0000422142Tyr0000221100Val9928284220.419.48278—bThe last row reflects totals.35351001006666100100145149a Lists numbers of methyl groups for each residue type.b The last row reflects totals. Open table in a new tab Solid-state NMR spectroscopy is an ideal structural tool for the characterization of elastin and its related peptides. The amorphous nature of native elastin and its inaccessibility to other high resolution structural methods it (and its related an ideal for characterization by solid-state solid-state NMR of native and elastin, as well as elastin have been reported K.A. J. Biol. PubMed Scopus Google Scholar, Biopolymers. 1976; PubMed Scopus (44) Google Scholar, Biopolymers. PubMed Scopus Google Scholar, Int. J. Biol. Macromol. 6: Scopus Google Scholar, A. Biophys. J. Full Text Full Text PDF PubMed Scopus Google Scholar, A. J. Chem. PubMed Scopus Google Scholar, R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, M. J. Chem. PubMed Scopus Google Scholar, J. Macromolecules. 2005; Scopus Google the and of the the reflects that elastin is likely composed of a in the hydrophobic domains with α-helical cross-linking regions. In addition, are in the nature of of the protein K.A. J. Biol. PubMed Scopus Google Scholar, A. Biophys. J. Full Text Full Text PDF PubMed Scopus Google Scholar, R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, Biochemistry. 14: PubMed Scopus (55) Google Scholar). with the of and on elastin, reported have on the amorphous native protein, which is assembled from the high molecular weight or the repeating polypeptides based on hydrophobic sequences found in both tropoelastin and insoluble and are to the native protein or the hydrophobic or However, the polypeptides described by Keeley and coworkers to be a and very the alternating nature of native hydrophobic and cross-linking domains the polypeptides to Furthermore, the of a experiments to for of a of structural by these two a of one-dimensional 13C CPMAS NMR experiments were The or as well as are of structure and editing in the of features in the regions of for the into the dynamics of the In this show that the substitution of the hinge region with the polyalanine results in the expected increase in α-helical However, changes to the hydrophobic domains were also new to the of protein folding in The for of and for elastin polypeptide and has been described in M. Bellingham C.M. Stahl R.J. Sitarz E.E. Lane C.J. Keeley F.W. J. Biol. Chem. 2003; 276: 48553-48562Abstract Full Text Full Text PDF Scopus (146) Google Scholar, 14Miao M. Cirulis J.T. Lee S. Keeley F.W. Biochemistry. 2005; 44: 14367-14375Crossref PubMed Scopus (89) Google Scholar). were into and were in with and This was in and for to protein a the was by for The was with in acid temperature by for polypeptides were from this by with 20 by a with in 20 the polypeptides were on a and by a acid and of polypeptides were determined by amino acid and molecular were by the of the for were determined by the of and polypeptides EP20-24-24 and EP20-24-24[23U] were in 1 and The were and on a of the to a ideal an apparent molecular of for EP20-24-24 and for EP20-24-24[23U]. The of the apparent molecular by to molecular identical to molecular by were for EP20-24-24 and for EP20-24-24[23U]. a that the was The indicate that the of these were on a with a were for EP20-24-24 and for EP20-24-24[23U]. were 13C were to the as an were with 20 For CP, a was by a or with a of were used for including of and for high were were with The used in experiments was or as were by the of J. Scholar). relaxation for the the or were The were as a of and to an a was the the for each were to the for that the for each was to and the other were The were to a of the of the as a of or sequences for spectral editing are included in by and coworkers J. A. Scopus Google Scholar). For the study, the cross-polarization with sequence was used to identify and methyl and spectral editing were determined as on on the cross-polarization of and a of These are similar to those reported L.B. J. Biomol. 2000; 18: PubMed Scopus Google Scholar). 13C with for and the of the 1 and 13C CPMAS NMR of EP20-24-24 and EP20-24-24[23U]. The were as a with its In EP20-24-24[23U], an was The was to the the In the region, were and The may be in by a as shown in the and were found three and and a In EP20-24-24, the of the and were and In EP20-24-24[23U], the numbers were and of α-helical were also found for both EP20-24-24[23U] EP20-24-24 for in are found of the in R. A. Macromolecules. Scopus Google Scholar, Macromolecules. Scopus Google Scholar, S. M. A. R. Chem. 1981; Scholar). Hence, the and were to the α-helical of the cross-linking domains. on the sequence of the or of the amino in EP20-24-24 and EP20-24-24[23U] were in hydrophobic domains, and the or were found in cross-linking domains. it that the found for EP20-24-24 in this expected for these sequences. substitution of the hinge region, the of was greatly This result is analogous to the determined by (14Miao M. Cirulis J.T. Lee S. Keeley F.W. Biochemistry. 2005; 44: 14367-14375Crossref PubMed Scopus (89) Google which also an increase in with the substitution of the was significantly more α-helical content in the of both The component was to the found in the hydrophobic domains. that a of M. J. Chem. PubMed Scopus Google Scholar, J. Macromolecules. 2005; Scopus Google or M. Tamburro A.M. Biopolymers. 2003; 70: PubMed Scopus Google is likely and is also by this have shown that of or are of J. C.M. Biochemistry. 2001; PubMed Scopus Google Scholar). solid-state NMR of elastin and elastin peptides have are considered to be A. Biophys. J. Full Text Full Text PDF PubMed Scopus Google Scholar, J. Macromolecules. 2005; Scopus Google Scholar, M. Tamburro A.M. Biopolymers. 2003; 70: PubMed Scopus Google Scholar, L.B. Biopolymers. 2001; 59: PubMed Scopus Google Scholar). EP20-24-24 and EP20-24-24[23U] are of a a of for the in for both The component of EP20-24-24[23U] was than EP20-24-24 However, these a was a structure Finally, for the region can be on the of for the various amino in EP20-24-24 and EP20-24-24[23U] R. A. Macromolecules. Scopus Google Scholar, Macromolecules. Scopus Google Scholar, S. M. A. R. Chem. 1981; Scholar, M. Tamburro A.M. Biopolymers. 2003; 70: PubMed Scopus Google Scholar, J. of for of of the Scholar). The amino acid in EP20-24-24 and EP20-24-24[23U] was with and of and were also The in the region were to of the The significant was for the of this of the of the was to The and were to of the amino and is that was in this region, and this of the is addressed in more in Finally, the of the were to methyl found in in and and In to the in an in of 13C CPMAS NMR between EP20-24-24 and the of in EP20-24-24 and EP20-24-24[23U] are are significant in the is a by EP20-24-24 from EP20-24-24[23U]. The are by the of the and in the The of in EP20-24-24 and EP20-24-24[23U] are and it is reasonable to that dynamics are also this The of features in the region as well as in the The EP20-24-24[23U] has more the EP20-24-24[23U] has more α-helical content than EP20-24-24 (14Miao M. Cirulis J.T. Lee S. Keeley F.W. Biochemistry. 2005; 44: 14367-14375Crossref PubMed Scopus (89) Google the of this is and also to the α-helical of EP20-24-24[23U]. In addition to the features to α-helical alanines, a significant also was in in the EP20-24-24[23U], and the and above were with Furthermore, the of is with two with J. Biomol. PubMed Scopus Google Scholar). Hence, it likely that the is to to other in This more likely results from a significant in and the structure of a residue type other than alanine. that have include and J. Biomol. PubMed Scopus Google Scholar). The has the as the one to the in Table are methyl groups in EP20-24-24 and in EP20-24-24[23U]. CPMAS are not to in and other it is reasonable to the of the two in the and that the of for each is 13C to this considered on its is of the amino acid types to be and or more in this include a one and features of likely of changes in structure. In a for such as EP20-24-24 and EP20-24-24[23U], has been one and with as one component is another is However, it that the EP20-24-24[23U] have the is such in the Furthermore, are found in the region of the it is that the and are likely to in between the two and with the In the and are found in experiments and are significantly more than the Hence, effort on the of the of these between on the of for the are in Table The and of the to region were a For the were a is a the of the various types to this the for each were between the two and very were For instance, the for was for EP20-24-24 and for EP20-24-24[23U]. The of to the α-helical of the was in EP20-24-24 and for EP20-24-24[23U]. For and the the were and for EP20-24-24 and and for EP20-24-24[23U]. Finally, the methyl and have of are for of elastin and A. Biophys. J. Full Text Full Text PDF PubMed Scopus Google Scholar, L.B. Biopolymers. 2001; 59: PubMed Scopus Google Scholar) and elastin mimetics M. Tamburro A.M. Biopolymers. 2003; 70: PubMed Scopus Google Scholar). of or these are are on this of EP20-24-24 and Open table in a new tab 13C of the in of in the for the in the These relaxation were determined to a of the in dynamics on the as to that the not significantly for the that the of the was For found in the region of were for EP20-24-24 and for EP20-24-24[23U]. For the and were and for EP20-24-24 and and for EP20-24-24[23U]. Finally, for the methyl and were and for EP20-24-24 and and for EP20-24-24[23U]. the of EP20-24-24[23U] longer than In such as the the between the two was of the of EP20-24-24 and Open table in a new tab The increase in the was also with the in EP20-24-24[23U] The longer in EP20-24-24[23U] that this polypeptide is more rigid than is the that the of the structure was not to the cross-linking domains, the substitution of the hinge region the changes in dynamics the including the hydrophobic domains. into the of the may be considered another of were constructed for each of the in EP20-24-24 and EP20-24-24[23U], as shown in and as a of and is for in in experiments was observed for and the were in these the and other the In the the to its or In the have significantly than the have a high of However, the of the methyl the these to be between the and the the of the or the to have for the EP20-24-24, with EP20-24-24[23U]. longer the of the EP20-24-24 which is the reported in the In these are with the for the of these into the of the that in the of the for EP20-24-24 and EP20-24-24[23U] for the and The and that are for methyl as The methyl for EP20-24-24 identical similar result of was also for the of EP20-24-24[23U]. The of and may be of the of the was to a The may be to a or of one of the hydrophobic amino J. of for of of the Scholar, J. Biomol. PubMed Scopus Google as In addition, methyl groups are found in this region J. of for of of the Scholar, J. Biomol. PubMed Scopus Google Scholar). the and in EP20-24-24 have very similar to be in EP20-24-24[23U], that the has that between the and methyl is that the of EP20-24-24[23U] has more methyl than that of for the of in the of in editing based on temperature and dynamics was by and coworkers J. A. 1993; Scopus Google Scholar, J. A. 1993; Scopus Google Scholar) and was shown more recently to be a tool for the of peptides and L.B. J. Biomol. 2000; 18: PubMed Scopus Google Scholar). a is with of is with cross-polarization with and methyl are cross-polarization with In the and are the and of the methyl region for these two was used for this The of the EP20-24-24 were found with and In of the EP20-24-24[23U] were observed The and were with a The of and to J. Macromolecules. 2005; Scopus Google Scholar, Biochemistry. 14: PubMed Scopus (55) Google and are with the determined for of the of the hinge region and with changes in of methyl as in the changes in overall on the of these EP20-24-24[23U] more α-helical alanines, a that is by the of the and the In addition, methyl groups with in the range in EP20-24-24 in EP20-24-24[23U], resulting in the of the to The as to the is a of the that does not well in the EP20-24-24 does in the or is a change in or that is by a in this the EP20-24-24 was also observed change in the methyl was observed this lower it is likely that the increase in in the EP20-24-24 is to a change of a of methyl The of the component from in EP20-24-24 to in EP20-24-24[23U]. this again, with the of in is in the two with of in these of with the of the in EP20-24-24, as The of the is with these editing shown in the in the CPMAS of EP20-24-24[23U] has significantly than However, an is by the that it is a in a region of the 13C and the is for the of the to to the of and is found in the J. of for of of the Scholar, J. Biomol. PubMed Scopus Google Scholar) and in separate of and peptides to the of this from its it to be more a methyl than the other as shown with the Finally, the provided in the more to the that the is likely to from the hydrophobic domains. that were observed between EP20-24-24 and EP20-24-24[23U], cross-polarization with more to the that the is to a change in the methyl one of these results or may not for a on its to evidence for the of the to the Finally, that the nature of this does not the that the is to another such as the or one of the However, indicate that the is the methyl to of the structure and functional models of elastin has effort into the organization of the hydrophobic domains, in the repeating However, these experiments show that the two domain types are not changes in the central or hinge of the cross-linking domains affect the structure the dynamics of the hydrophobic regions. The substitution in the hinge region results in the expected of to α-helical However, that is also a significant in identify this the and peptide were used in this In addition, were and spectral editing experiments were this the likely of this is the methyl of or which are found in the hydrophobic domains. is a that the may be to another such as the of the alanines. The to this be of amino such as the However, based on the of the of the to the found in hydrophobic domains reasonable and In addition to the and its of the hinge region was with a change in 13C The relaxation are with the of in properties between the these NMR results indicate that the EP20-24-24 polypeptide more than the unhinged These experiments indicate that EP20-24-24 has and a of than the unhinged EP20-24-24[23U]. is likely that these two characteristics are the of the hinged polypeptide EP20-24-24 a of to be this type of is a in elastin peptides and in the native protein and is one of the key features of This the phenomenon of coacervation or in this this hinge is replaced by a polyalanine the of between hydrophobic domains of a peptide are greatly these hydrophobic domains with those of a or as a or coacervation is This is with of coacervation EP20-24-24[23U] lower than EP20-24-24 (14Miao M. Cirulis J.T. Lee S. Keeley F.W. Biochemistry. 2005; 44: 14367-14375Crossref PubMed Scopus (89) Google Scholar). significant effort has been placed in the structural characteristics of the hydrophobic of elastin, this more evidence that the sequences in cross-linking domains also a key role in the overall structure of the these results the for a new of experiments that the between domain types and that a for elastin structure is long A. for in of peptides related to this with

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