Residues in the Human Corticosteroid-binding Globulin Reactive Center Loop That Influence Steroid Binding before and after Elastase Cleavage

Corticosteroid-binding globulin (CBG) is a non-inhibitory serine proteinase inhibitor (serpin) that transports cortisol and progesterone in blood. Crystal structures of rat CBG and a thrombin-cleaved human CBG:anti-trypsin (Pittsburgh) chimera show how structural transitions after proteolytic cleavage of the CBG reactive center loop (RCL) could disrupt steroid binding. This ligand release mechanism is assumed to involve insertion of the cleaved RCL into the β-sheet A of the serpin structure. We have, therefore, examined how amino acid substitutions in the human CBG RCL influence steroid binding before and after its cleavage by neutrophil elastase. Elastase-cleaved wild-type CBG or variants with substitutions at P15 and/or P16 (E334G/G335N or E334A) lost steroid binding completely, whereas deletion of Glu-334 resulted in no loss of steroid binding after RCL cleavage, presumably because this prevents its insertion into β-sheet A. Similarly, the steroid binding properties of CBG variants with substitutions at P15 (G335P), P14 (V336R), or P12 (T338P) in the RCL hinge were largely unaffected after elastase cleavage, most likely because the re-orientation and/or insertion of the cleaved RCL was blocked. Substitutions at P10 (G340P, G340S) or P8 (T342P, T342N) resulted in a partial loss of steroid binding after proteolysis which we attribute to incomplete insertion of the cleaved RCL. Remarkably, several substitutions (E334A, V336R, G340S, and T342P) increased the steroid binding affinities of human CBG even before elastase cleavage, consistent with the concept that CBG normally toggles between a high affinity ligand binding state where the RCL is fully exposed and a lower affinity state in which the RCL is partly inserted into β-sheet A. Corticosteroid-binding globulin (CBG) is a non-inhibitory serine proteinase inhibitor (serpin) that transports cortisol and progesterone in blood. Crystal structures of rat CBG and a thrombin-cleaved human CBG:anti-trypsin (Pittsburgh) chimera show how structural transitions after proteolytic cleavage of the CBG reactive center loop (RCL) could disrupt steroid binding. This ligand release mechanism is assumed to involve insertion of the cleaved RCL into the β-sheet A of the serpin structure. We have, therefore, examined how amino acid substitutions in the human CBG RCL influence steroid binding before and after its cleavage by neutrophil elastase. Elastase-cleaved wild-type CBG or variants with substitutions at P15 and/or P16 (E334G/G335N or E334A) lost steroid binding completely, whereas deletion of Glu-334 resulted in no loss of steroid binding after RCL cleavage, presumably because this prevents its insertion into β-sheet A. Similarly, the steroid binding properties of CBG variants with substitutions at P15 (G335P), P14 (V336R), or P12 (T338P) in the RCL hinge were largely unaffected after elastase cleavage, most likely because the re-orientation and/or insertion of the cleaved RCL was blocked. Substitutions at P10 (G340P, G340S) or P8 (T342P, T342N) resulted in a partial loss of steroid binding after proteolysis which we attribute to incomplete insertion of the cleaved RCL. Remarkably, several substitutions (E334A, V336R, G340S, and T342P) increased the steroid binding affinities of human CBG even before elastase cleavage, consistent with the concept that CBG normally toggles between a high affinity ligand binding state where the RCL is fully exposed and a lower affinity state in which the RCL is partly inserted into β-sheet A. Corticosteroid-binding globulin (CBG) 2The abbreviations used are: CBG, corticosteroid-binding globulin; AAT, α1-anti-trypsin; DCC, dextran-coated charcoal; RCL, reactive center loop; S→R, stressed to relaxed.2The abbreviations used are: CBG, corticosteroid-binding globulin; AAT, α1-anti-trypsin; DCC, dextran-coated charcoal; RCL, reactive center loop; S→R, stressed to relaxed. is the major carrier protein for natural glucocorticoids (cortisol and corticosterone) and progesterone in blood (1Hammond G.L. Endocr. Rev. 1990; 11: 65-79Crossref PubMed Scopus (263) Google Scholar), and it regulates the bioavailability of steroids that control numerous physiological processes including reproduction, inflammation, stress responses, and tissue development (2Hammond G.L. Obstet. Gynecol. Clin. North Am. 2002; 29: 411-423Abstract Full Text Full Text PDF PubMed Scopus (59) Google Scholar). Because CBG binds up to 90% of the glucocorticoids in blood plasma, it serves as a reservoir of anti-inflammatory steroids that can be released at their sites of action (3Breuner C.W. Orchinik M. J. Endocrinol. 2002; 175: 99-112Crossref PubMed Scopus (357) Google Scholar). The latter concept was proposed when it was discovered that human CBG exhibits remarkable sequence identity with the archetypal serine proteinase inhibitor, α1-anti-trypsin (AAT), and was based on the realization that CBG might also be a target of specific classes of proteinases (4Hammond G.L. Smith C.L. Goping I.S. Underhill D.A. Harley M.J. Reventos J. Musto N.A. Gunsalus G.L. Bardin C.W. Proc. Natl. Acad. Sci. U. S. A. 1987; 84: 5153-5157Crossref PubMed Scopus (233) Google Scholar). The close structural relationship between CBG and AAT defines it as a clade A serine proteinase inhibitor (serpin) family member (5Law R.H. Zhang Q. McGowan S. Buckle A.M. Silverman G.A. Wong W. Rosado C.J. Langendorf C.G. Pike R.N. Bird P.I. Whisstock J.C. Genome Biology. 2006; 7: 216Crossref PubMed Scopus (475) Google Scholar). Many of these serpin A family members, including CBG, are encoded by genes in the human 14q21.1 chromosome cluster and are thought to have arisen by gene duplication to produce serpins with similar properties and physiological functions (6Gettins P.G. Chem. Rev. 2002; 102: 4751-4804Crossref PubMed Scopus (983) Google Scholar). Unlike most clade A serpins, CBG is not known to act as a proteinase inhibitor but appears to be a suicide substrate of specific proteinases and is particularly sensitive to attack by neutrophil elastase, the activity of which is normally controlled by AAT (7Hammond G.L. Smith C.L. Underhill D.A. J. Steroid Biochem. Mol. Biol. 1991; 40: 755-762Crossref PubMed Scopus (108) Google Scholar). Structurally, serpins are defined by a single core domain of three β-sheets (termed A, B, and C) and 8–9 α-helices (termed hA-hI) (6Gettins P.G. Chem. Rev. 2002; 102: 4751-4804Crossref PubMed Scopus (983) Google Scholar). For inhibitory serpins in the native state, a reactive center loop (RCL) is fully exposed for target proteinases to recognize and interact. Upon cleavage by proteinase, the RCL is inserted into β-sheet A to form a novel β-strand (s4A), which results in a profound “stressed to relaxed” (S→R) conformational transition (8Irving J.A. Pike R.N. Lesk A.M. Whisstock J.C. Genome Res. 2000; 10: 1845-1864Crossref PubMed Scopus (507) Google Scholar). The S→R transition is associated with an increase in thermostability and is crucial for the inhibitory mechanism that yields the serpin-proteinase the are the most of serpins with the (6Gettins P.G. Chem. Rev. 2002; 102: 4751-4804Crossref PubMed Scopus (983) Google Scholar), and the for this are not fully proposed that the serpin by CBG and the globulin to control release at their sites of action after the RCL is cleaved by proteinases PubMed Scopus Google G.L. Smith C.L. N.A. J. Clin. Endocrinol. 1990; PubMed Scopus Google S. J. Clin. Endocrinol. 2002; PubMed Scopus Google A. J. J. Clin. Endocrinol. 2000; PubMed Scopus Google Scholar). This is based on that the S→R conformational transition of CBG is by a increase in thermostability PubMed Scopus Google and in steroid binding affinity PubMed Scopus Google G.L. Smith C.L. N.A. J. Clin. Endocrinol. 1990; PubMed Scopus Google after cleavage by neutrophil elastase. we the of rat CBG a native serpin with the RCL fully exposed the β-sheet A Underhill G.L. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). The of a thrombin-cleaved human chimera in which the RCL of human CBG was with an AAT sequence A. J. Mol. Biol. PubMed Scopus Google Scholar), presumably to cleavage by this the cleaved AAT RCL was fully into the β-sheet A of CBG, and the in cortisol to the that the of the cleaved chimera a that that of native CBG A. J. Mol. Biol. PubMed Scopus Google Scholar). elastase cleavage of CBG results in an loss of steroid binding that be by an of steroid ligand PubMed Scopus Google G.L. Smith C.L. N.A. J. Clin. Endocrinol. 1990; PubMed Scopus Google Scholar), and and high ligand might have the binding of cortisol with affinity to the cleaved the of the CBG RCL with the AAT (Pittsburgh) sequence have steroid binding because have that human AAT RCL have increased or ligand binding affinities A. Biochem. J. 2002; PubMed Google Scholar). also be that the proteolytic cleavage in human AAT J.C. Lesk A.M. J. Mol. Biol. 2000; PubMed Scopus (59) Google in to that in human CBG, which to the and in the AAT RCL PubMed Scopus Google Scholar). the cleaved RCL of human CBG is that of AAT or the AAT (Pittsburgh) and the and of the cleaved RCL in the thrombin-cleaved human chimera A. J. Mol. Biol. PubMed Scopus Google are likely in human of the human chimera A. J. Mol. Biol. PubMed Scopus Google also to the that a of the RCL into and of β-sheet A the release of but for this is the in a we have specific the RCL of human CBG and how this its proteolytic cleavage by neutrophil elastase in to its cortisol binding This not to the RCL that control the S→R transition of CBG, which results in but that partial insertion of the RCL the human CBG β-sheet A an on its cortisol binding were in and at with CBG and the human CBG (4Hammond G.L. Smith C.L. Goping I.S. Underhill D.A. Harley M.J. Reventos J. Musto N.A. Gunsalus G.L. Bardin C.W. Proc. Natl. Acad. Sci. U. S. A. 1987; 84: 5153-5157Crossref PubMed Scopus (233) Google S. G.L. J. Biol. Chem. Full Text PDF PubMed Google was into a were on the wild-type human CBG with the to the The and used for are in were to that the used for in a of and wild-type or human were at in and with of as by the were at a of and in the of for were to with the were for in high The were in a and cortisol at and to on a protein to the for neutrophil elastase was in and elastase were with of and of elastase for at as G.L. Smith C.L. N.A. J. Clin. Endocrinol. 1990; PubMed Scopus Google Scholar). were by after by in the of and neutrophil elastase human CBG in a single and its by which can be by as G.L. Smith C.L. N.A. J. Clin. Endocrinol. 1990; PubMed Scopus Google Scholar). were by and and to a with in were with CBG at a G.L. J. Endocrinol. PubMed Scopus Google Scholar). were with a and by to Steroid was steroids were The steroid binding of of by were by a as the ligand and dextran-coated as a G.L. Clin. PubMed Scopus Google Scholar). the steroid binding of CBG before and after elastase cleavage, protein was of steroid by with for at and with an of for at of the were to elastase cleavage, as whereas the was the the of elastase. of cleaved and were to and the was and used to the of in after of steroid with for at G.L. Clin. PubMed Scopus Google Scholar). The of were also by the of the cleaved or to for at G.L. Clin. PubMed Scopus Google Scholar). binding of wild-type CBG and the CBG variants were by as the ligand G.L. Clin. PubMed Scopus Google Scholar). Substitutions at P16 and P15 in the CBG RCL of the CBG including human rat and human AAT that their RCL are The of in the RCL is in to the proteinase cleavage of human AAT the elastase cleavage sites of human CBG and AAT are in their neutrophil elastase AAT in the as the CBG cleavage at the at in human AAT is M.J. S. J. J. Clin. 1987; PubMed Scopus Google Scholar). The amino acid substitutions we have the CBG RCL are also in to the cleavage in AAT with a of how the cleaved CBG RCL is thought to between the and We examined the of several substitutions the of the RCL to and on Glu-334 and in human CBG to of the hinge that of the RCL after proteinase cleavage The amino of the CBG RCL is not and in human CBG is by Glu-334 at P16 the at P15 in human CBG is in it that the at P16 in an to in human CBG in the RCL to after cleavage Underhill G.L. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). therefore, the P16 and P15 of the human CBG RCL into the in rat CBG, and and this for its to be cleaved by neutrophil elastase and to steroid before and after elastase in the of wild-type CBG, it is that these amino acid substitutions not elastase cleavage, as by or influence the loss of steroid binding that after proteolysis of the RCL of human CBG The show the in the of human CBG by consistent with the loss of the that are not by after cleavage by elastase G.L. Smith C.L. Underhill Biochem. Res. 1990; PubMed Scopus Google Scholar). The steroid binding of CBG were also with wild-type CBG in a to the of their sites before and after with elastase for this an of binding it can be after elastase proteolysis of CBG cleavage of the RCL, which can be in by the of wild-type CBG and the human CBG elastase cleavage results in a in the of to the of A and The of that after the elastase likely the of the steroid binding of and the by the of cleaved with binding this we the at of as a of the at the and this that the of these after elastase cleavage is that for the of A and therefore, that the after elastase cleavage, binding to a of a the cleaved which and which be to the of Glu-334 and to the loss of steroid binding the CBG after elastase cleavage, we on Glu-334 and it or it with an Because the acid at in human CBG is in serpin structures deletion of Glu-334 that the be to the as it is in rat CBG The loss of Glu-334 no on the cleavage of CBG by elastase but its binding after elastase cleavage was This was in of the of its binding when in of the of or a of the at after when the Glu-334 in human CBG was with an and this was cleaved by elastase it the wild-type protein and lost of its binding and We the P15 with to the of the RCL that is to as the conformational in this RCL this CBG was we that it its steroid binding activity after proteolytic cleavage A and and this was in the and variants and were after elastase cleavage, of and we attribute this to the loss of an the cleaved RCL. Substitutions at P14 and P12 of the CBG RCL on Steroid we the at P14 of human CBG with a this not influence its cleavage by elastase cleavage of the not its steroid binding or the of its binding We also the at P12 with a or with an at because this an as in the the rat CBG RCL in the of the CBG the and substitutions no on the proteolytic cleavage of the RCL by elastase and their steroid binding to even increase after elastase cleavage the of the and human CBG the latter was in of the of their binding sites before and after elastase cleavage and in these it appears that the of the is their and of and P14 P12 and human CBG was to or at and the were for or at before to of the were also on a to the cleavage by elastase, as in A, B, The results are as in or the of the at of in to the at of was used to the and the for the binding were CBG with Substitutions at P10 and P8 in the RCL Steroid after we at P10 with a or serine rat CBG and at P8 with or in rat the cortisol binding of these variants (G340P, G340S, and T342N) were after elastase cleavage the of the native and of these variants were in the binding of the G340S, and CBG variants were and their were increased after elastase cleavage, that the steroid binding properties of these CBG variants are not when their are of and P10 and P8 human CBG was to or at and the were for or at before of the were also on a to the cleavage by elastase, as in A, B, The results are as in or the of the at of in to the at of was used to the and the for the binding were We also that the to be cleaved by elastase at the used in Because this is to the elastase cleavage in the CBG RCL, we assumed that it might the proteolytic we the elastase for and and that for and were cleaved when with the the loss in cortisol binding of the also between the and with elastase therefore, the steroid binding properties of the before and to elastase and a increase in the of the protein with increased of proteolysis Substitutions in the RCL of CBG Steroid the amino acid substitutions we into the RCL of human CBG have on the steroid binding properties of the native before elastase cleavage, we with wild-type CBG in the as as by the affinities of most CBG variants for were that of wild-type CBG in these it was that the V336R, G340S, and variants This that these variants have a affinity for cortisol when with the wild-type and this was by which that these CBG variants with with binding of and when with wild-type CBG proposed that several the RCL of serpins are in the conformational that after with their target the hinge of the the of β-sheet the the center of β-sheet and the including and (8Irving J.A. Pike R.N. Lesk A.M. Whisstock J.C. Genome Res. 2000; 10: 1845-1864Crossref PubMed Scopus (507) Google Scholar). these the hinge is thought to the for conformational in the RCL its into the serpin β-sheet A structural after proteolysis (8Irving J.A. Pike R.N. Lesk A.M. Whisstock J.C. Genome Res. 2000; 10: 1845-1864Crossref PubMed Scopus (507) Google PubMed Scopus Google Scholar). The RCL is in its and and in the of inhibitory serpins this is to an for with their target proteinases (8Irving J.A. Pike R.N. Lesk A.M. Whisstock J.C. Genome Res. 2000; 10: 1845-1864Crossref PubMed Scopus (507) Google 1987; PubMed Scopus Google Scholar). is a in the hinge of inhibitory serpins, with P15 by P14 by a or and with at P12 to (6Gettins P.G. Chem. Rev. 2002; 102: 4751-4804Crossref PubMed Scopus (983) Google J.A. Pike R.N. Lesk A.M. Whisstock J.C. Genome Res. 2000; 10: 1845-1864Crossref PubMed Scopus (507) Google Scholar). of inhibitory and non-inhibitory serpins that P12 to in the inhibitory serpins have a of at and the are or whereas non-inhibitory serpins have or no at these (6Gettins P.G. Chem. Rev. 2002; 102: 4751-4804Crossref PubMed Scopus (983) Google Scholar). inhibitory serpins, the of RCL insertion to the cleavage the of the (6Gettins P.G. Chem. Rev. 2002; 102: 4751-4804Crossref PubMed Scopus (983) Google Scholar). the of the RCL and particularly the that is a of the of loop of this in that it the for this conformational transition and most serpins a acid at with a in a to a in and a in (8Irving J.A. Pike R.N. Lesk A.M. Whisstock J.C. Genome Res. 2000; 10: 1845-1864Crossref PubMed Scopus (507) Google Scholar). This of the is because at in AAT Biol. PubMed Scopus Google and J. J. A. A. J.A. PubMed Scopus Google disrupt the and these to the acid in serpin an and it is that it the of the because it is in the in cleaved and serpins, as in the native rat CBG Underhill G.L. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google and cleaved human chimera A. J. Mol. Biol. PubMed Scopus Google cleaved serpins, the amino of is to a which in human CBG the P16 and P15 of the RCL Underhill G.L. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). that of the P16 and P15 of human CBG with the and in rat CBG no on the steroid binding properties of this elastase cleavage when with human wild-type This that the at P16 in for the P15 in and the in the of these between is to the of the cleaved rat CBG RCL as a β-sheet Underhill G.L. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). we the Glu-334 at P16 in human CBG with and the at P15 with the lost its cortisol binding activity in the as wild-type CBG after elastase cleavage, the cortisol binding properties of the not before or after elastase This that the RCL of the even after it is cleaved and the that this in the with to the of the cleaved RCL. deletion of Glu-334 in human CBG resulted in a that fully its steroid binding activity after elastase cleavage, which that its RCL after elastase it also be that when the RCL normally the β-sheet A, the of the core of the whereas the of the in the cleaved RCL Underhill G.L. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). therefore, that the deletion of Glu-334 at the of the RCL not with its but its with to the β-sheet A and its as a novel The of inhibitory serpin-proteinase results in insertion of the RCL, which the proteinase to the of the serpin (6Gettins P.G. Chem. Rev. 2002; 102: 4751-4804Crossref PubMed Scopus (983) Google Scholar). the of RCL insertion the of the inhibitory and it is not that a P14 an in the RCL as its is the to the core of the cleaved serpin (6Gettins P.G. Chem. Rev. 2002; 102: 4751-4804Crossref PubMed Scopus (983) Google Scholar). The of P14 in the of the loop insertion was by a of AAT that a in of the at P14 J.A. P.G. PubMed Scopus Google and was in of variants in which the P14 was by a of D.A. S. J. Biol. Chem. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). the latter the in the of and the for RCL insertion were by substitutions with amino of which the D.A. S. J. Biol. Chem. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). the of a cleaved with a at P14 that the is not in incomplete insertion Biol. PubMed Scopus Google Scholar). on a non-inhibitory serpin that an at P14 and the loop insertion mechanism J. Mol. Biol. 1990; PubMed Scopus Google Scholar), that when this P14 in is with the is by an increased RCL insertion and partial insertion of the cleaved RCL J.A. J. D.A. P.G. PubMed Scopus Google Scholar). the of the cleaved that loop insertion can this single hinge M. M. J. Mol. Biol. 2002; PubMed Scopus Google Scholar). are in with that of the P14 in human CBG with not cleavage of its RCL by elastase or its steroid binding properties after cleavage, presumably because the at P14 prevents the and/or insertion of the cleaved RCL. the we the P12 in human CBG with a as in rat CBG because rat CBG a in the to in human CBG, we also the at in human CBG with an acid in to the a human CBG that also have a sequence in the of these variants that are cleaved by neutrophil elastase but that this not their steroid binding of human CBG that it is most CBG in the of the we attribute this to a loss proteolysis because the steroid binding properties of the are not lost and even to be after RCL the of an the RCL not its cleavage by elastase, that substitutions at and P12 of human CBG, which were to the rat CBG to RCL insertion after elastase The that the was to this the of CBG RCL have in with β-sheet A to insertion of the cleaved RCL an to of their by proteinases 1987; PubMed Scopus Google Scholar). we recognize that a is at P12 in serpins (6Gettins P.G. Chem. Rev. 2002; 102: 4751-4804Crossref PubMed Scopus (983) Google as as in rat CBG, are to and how the cleaved RCL of rat CBG β-sheet A. to the P10 in serpin to in the inhibitory functions of serpins, as by the inhibitory properties of variants of and inhibitor (6Gettins P.G. Chem. Rev. 2002; 102: 4751-4804Crossref PubMed Scopus (983) Google Scholar). also that of at P10 in AAT to its inhibitory properties PubMed Scopus Google Scholar). Because the P10 and P8 in human CBG and are to the elastase cleavage of human CBG in AAT, we with a or the in the rat CBG The results of these are of because the steroid binding affinities of these variants are even after appears to be RCL cleavage, and this is most with to the This that their are partly inserted after elastase of is the that of these variants an with the and variants in that their affinities for cortisol are that of wild-type human CBG even before elastase that the or of their RCL the This the concept that the RCL of CBG normally toggles between conformational Underhill G.L. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google that a state in which the RCL is fully and an state in which the RCL is as for the of the J.A. Proc. Natl. Acad. Sci. U. S. A. 2002; PubMed Scopus Google and M. Pike R.N. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google this be consistent with the concept that a fully exposed RCL, as most likely at in the of the and in CBG with steroid binding affinities because the RCL between the conformational also the that the and most P14 inserted after RCL cleavage, the with at the is at (6Gettins P.G. Chem. Rev. 2002; 102: 4751-4804Crossref PubMed Scopus (983) Google Scholar). most serpins, P8 is by a with a (6Gettins P.G. Chem. Rev. 2002; 102: 4751-4804Crossref PubMed Scopus (983) Google Scholar). the of binding it that the at P8 loop insertion the of the β-sheet A and that in most serpins the by a in the lower of and is by the of a P8 of the loop A. Proc. Natl. Acad. Sci. U. S. A. 2006; PubMed Scopus Google Scholar). is no for results it because the P8 in human CBG with appears to in loop insertion The S→R conformational transition of serpins is to their and have to in as the and hinge of their (5Law R.H. Zhang Q. McGowan S. Buckle A.M. Silverman G.A. Wong W. Rosado C.J. Langendorf C.G. Pike R.N. Bird P.I. Whisstock J.C. Genome Biology. 2006; 7: 216Crossref PubMed Scopus (475) Google Scholar). amino acid substitutions in the RCL hinge of serpins with their inhibitory and serpin have to as at P10 of S. M. PubMed Scopus Google M. A.M. J. Clin. 84: PubMed Scopus Google D.A. M. M. J. 1991; PubMed Scopus Google as as at P10 A. M. J. Biol. Chem. Full Text PDF PubMed Google Scholar), P12 M. J. Biol. Chem. 1991; Full Text PDF PubMed Google Scholar), and P14 J. J. PubMed Scopus Google of The rat CBG Underhill G.L. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google how several CBG variants could for in steroid binding Underhill G.L. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar), including human CBG variants G.L. PubMed Scopus Google C.L. G.L. J. Steroid Biochem. Mol. Biol. PubMed Scopus Google in and A. G.L. M. J. Clin. Endocrinol. 2000; Google in as as the rat CBG C.L. G.L. J. Biol. Chem. 1991; Full Text PDF PubMed Google in and the CBG M. G.L. PubMed Scopus Google in of these CBG were because steroid binding and the that CBG variants with high affinity sites that their after elastase cleavage of the RCL. we have defined the between the proteolytic cleavage of the human CBG RCL and the of its we have a crucial for hinge at and P8 insertion of the cleaved RCL as of the S→R conformational transition that in the that human CBG in conformational with steroid binding affinities before and after cleavage by of its target neutrophil elastase. We A. and of for and

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