PMID: 3768339Sep 9, 1986Paper

Peptide models of protein metastable binding sites: competitive kinetics of isomerization and hydrolysis

Biochemistry
S A KhanB W Erickson

Abstract

alpha 2-Macroglobulin and the complement components C3 and C4 each contain a metastable binding site that is essential for covalent attachment. Two cyclic peptides are useful models of these unusual protein sites. Five-membered lactam 1 (CH3CO-Gly-Cys-Gly-Glu-Glp-Asn-NH2) contains an internal residue of pyroglutamic acid (Glp). Fifteen-membered thiolactone 2 (CH3CO-Gly-Cys-Gly-Glu-Glu-Asn-NH2 15-thiolactone) contains a thiol ester bond between Cys-2 and Glu-5. These isomeric hexapeptides are spontaneously interconverted in water. Competing with the two isomerization reactions are three reactions involving hydrolysis of 1 and 2. These five processes were found to occur simultaneously under physiologic conditions (phosphate-buffered saline, pH 7.3, 37 degrees C). Best estimates of the five rate constants for these apparent first-order reactions were obtained by comparing the observed molar percentages of peptides 1-4 with those calculated from a set of exponential equations. Both isomerization reactions (ring expansion of 1 to 2, k1 = 6.4 X 10(-5) s-1; ring contraction of 2 to 1, k-1 = 69 X 10(-5) s-1) proceeded faster than any of the hydrolysis reactions: alpha-cleavage of 1 with fragmentation to form dipeptide 3 (k2 = 3.3 X 10(...Continue Reading

References

Sep 1, 1979·Proceedings of the National Academy of Sciences of the United States of America·R P Swenson, J B Howard
Jan 1, 1980·Advances in Immunology·H J Müller-Eberhard, R D Schreiber
Jan 12, 1981·FEBS Letters·L Sottrup-JensenS Magnusson
Apr 1, 1981·Proceedings of the National Academy of Sciences of the United States of America·J B Howard
May 1, 1981·The Biochemical Journal·G S SalvesenA J Barrett
Feb 1, 1982·Proceedings of the National Academy of Sciences of the United States of America·M L ThomasB F Tack
Jan 1, 1983·Annals of the New York Academy of Sciences·B W Erickson, S A Khan
Jun 1, 1983·Molecular Immunology·T E HugliB W Erickson
Oct 1, 1980·Proceedings of the National Academy of Sciences of the United States of America·B F TackJ W Prahl
Dec 1, 1981·Proceedings of the National Academy of Sciences of the United States of America·R A HarrisonB F Tack

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Citations

Jul 13, 2006·Journal of Molecular Biology·Folmer FredslundLars Sottrup-Jensen
Oct 19, 2016·Nature Chemical Biology·John JanetzkoSuzanne Walker
Mar 30, 2017·The Journal of Biological Chemistry·Daniel J EchelmanJulio M Fernández
Oct 23, 2014·The Journal of Biological Chemistry·John Janetzko, Suzanne Walker
Dec 1, 2014·Biophysics Reviews·Marni Williams, Richard Baxter

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