The pH-Dependence of the Equilibrium between the Fast- and Slow-Folding Forms of Bovine Prothrombin Fragment 1: A Role for pH-Induced Self-Association?

Examination of the pH- and ionic strength (μ)-dependence of the equilibrium between fast- and slow-folding forms of bovine prothrombin fragment 1 reveals a sharp dependence of Keq ([% fast-folding form]/[% slow-folding form]) and % fluorescence quenching (%Q) on pH at low μ, and the absence of a pH-...

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Bibliographic Details
Published in:	Biochemical and biophysical research communications Vol. 206; no. 2; pp. 742 - 747
Main Authors:	Malhotra, O.P., Chang, H.Y.C., Koehler, K.A.
Format:	Journal Article
Language:	English
Published:	United States Elsevier Inc 17-01-1995
Subjects:	Animals Buffers Cattle Hydrogen-Ion Concentration Kinetics Osmolar Concentration Peptide Fragments - chemistry Peptide Fragments - metabolism Protein Folding Protein Precursors - chemistry Protein Precursors - metabolism Prothrombin - chemistry Prothrombin - metabolism Spectrometry, Fluorescence
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Summary:	Examination of the pH- and ionic strength (μ)-dependence of the equilibrium between fast- and slow-folding forms of bovine prothrombin fragment 1 reveals a sharp dependence of Keq ([% fast-folding form]/[% slow-folding form]) and % fluorescence quenching (%Q) on pH at low μ, and the absence of a pH-dependence of Keq at high μ (0.1 M NaCl) and much reduced pH-dependence of %Q, suggesting that the ionization process is coupled to other processes, such as self-association. The observed low μ pH effect on Keq amounts to a 10% increase in the % of the fast-folding form of prothrombin at low pH. We hypothesize the existence of a pH-dependent self-association of bovine prothrombin fragment 1. This process is associated with a conformation change involving an ionizing group with pKa in the neighborhood of 6.5 and a change in Keq from 0.27 to 0.45.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0006-291X 1090-2104
DOI:	10.1006/bbrc.1995.1105