Dissociation of light chains from cardiac myosin.
نویسندگان
چکیده
The substrate, ATP, protects the active site of cardiac myosin during a 10-min treatment at 37 "C and neutral pH in the absence of divalent cations; under these conditions there is an approximate 20 % dissociation of light chain C1 and 60 % loss of light chain CZ with no corresponding decrease in myosin ATPase activity. Higher temperatures, the absence of divalent cations, increased treatment time, and low protein concentration were conducive to light chain dissociation; loss of light chains did not appear to be influenced by increments of pH from 7.0 to 9.0. On the other hand, a decrease in protein concentration and an increase in both duration of exposure at 37°C and an alkaline pH caused a decrease in myosin ATPase activity. Concomitant with the dissociation of cardiac myosin light chains, particularly light chain C2, there was a corresponding loss in the number of high-affinity calcium binding sites. When the dissociated light chains were recombined with lightchain-deficient myosin, reassociation took place and the number of high-affinity calcium binding sites were regained. Reassociation of light chains with light-chain-deficient myosin did not restore diminished light-chain-deficient myosin ATPase activity. There is a shift in the pH optimum of myosin at 37 "C in the absence of divalent cations, where conditions used for light chain dissociation are employed. The presence of calcium prevents light chain dissociation, helps retain myosin ATPase activity at 37 "C and prevents a shift in the pH optimum.
منابع مشابه
Comparative sequence of myosin light chains from normal and hypertrophied human hearts.
Myosin light chains from normal and hypertrophied human hearts were partially sequenced in order to see whether structural modifications of these light subunits could provide a molecular basis for the changes observed in heart properties and in myosin enzymatic activity. Normal light chains were prepared form hearts taken at autopsy, weighing 350 g or less and apparently devoid of myocardial di...
متن کاملDissociation of myosin light chains and decreased myosin ATPase activity with acidification of synthetic myosin filaments: possible clues to the fate of myosin in myocardial ischemia and infarction.
متن کامل
Formation and characterization of myosin hybrids containing essential light chains and heavy chains from different muscle myosins.
Light chain exchange in 4.7 M NH4Cl was used to hybridize the essential light chain of cardiac myosin with the heavy chain of fast muscle myosin subfragment 1, S-1. The actin-activated ATPase properties of this hybrid were compared to those of the two fast S-1 isoenzymes, S-1(A1), fast muscle subfragment 1 which contains only the alkali-1 light chain, and S-1(A2), fast muscle myosin subfragment...
متن کاملSubunit interactions of skeletal muscle myosin and myosin subfragment 1. Evidence for heavy chain-alkali light chain association-dissociation equilibrium.
Modification of the free alkali light chains of myosin by iodoacetylation results in a much lower extent of exchange into myosin subfragment 1 by the thermal hybridization procedure (Burke, M., and Sivaramakrishnan, M. (1981) Biochemistry 20, 5908-5913). As reported by others (Wagner, P. D., and Stone, D. B. (1983) J. Biol. Chem. 258, 8876-8882), free alkali light chains modified by iodoacetate...
متن کاملIdentification of sequences necessary for the association of cardiac myosin subunits
To begin to understand the nature of myosin subunit assembly, we determined the region of a vertebrate sarcomeric myosin heavy chain required for binding of light chain 1. We coexpressed in Escherichia coli segments of the rat alpha cardiac myosin heavy chain which spanned the carboxyl terminus of subfragment 1 and the amino terminus of subfragment 2 with a full-length rat cardiac myosin light ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- European journal of biochemistry
دوره 92 2 شماره
صفحات -
تاریخ انتشار 1978