THE PH-DEPENDENCE OF THE EQUILIBRIUM BETWEEN THE FAST-FOLDING AND SLOW-FOLDING FORMS OF BOVINE PROTHROMBIN FRAGMENT-1 - A ROLE FOR PH-INDUCED SELF-ASSOCIATION
Op. Malhotra et al., THE PH-DEPENDENCE OF THE EQUILIBRIUM BETWEEN THE FAST-FOLDING AND SLOW-FOLDING FORMS OF BOVINE PROTHROMBIN FRAGMENT-1 - A ROLE FOR PH-INDUCED SELF-ASSOCIATION, Biochemical and biophysical research communications, 206(2), 1995, pp. 742-747
Examination of the pH- and ionic strength (mu)-dependence of the equil
ibrium between fast- and slow-folding forms of bovine prothrombin frag
ment 1 reveals a sharp dependence of K-eq ([% fast-folding form]/[% sl
ow-folding form]) and % fluorescence quenching (%Q) on pH at low mu, a
nd the absence of a pH-dependence of K-eq at high mu (0.1 M NaCl) and
much reduced pH-dependence of %Q, suggesting that the ionization proce
ss is coupled to other processes, such as self-association. The observ
ed low mu pH effect on K-eq amounts to a 10% increase in the % of the
fast-folding form of prothrombin at low pH. We hypothesize the existen
ce of a pH-dependent self-association of bovine prothrombin fragment 1
. This process is associated with a conformation change involving an i
onizing group with pK(a) in the neighborhood of 6.5 and a change in K-
eq from 0.27 to 0.45. (C) 1995 Academic Press, Inc.