Microheterogeneity around the reactive lysine residue in the myosin heavy chain from rabbit skeletal muscle

H Komatsu,K Tawada

doi:10.1016/s0021-9258(19)85289-4

Abstract

A molecule of myosin subfragment 1 (S1) from rabbit skeletal muscle has one highly reactive lysine residue, Lys-83 (RLR), in the heavy chain, which is rapidly and stoichiometrically modified by trinitrobenzenesulfonate. Our previous kinetic study (Komatsu, H., Emoto, Y., and Tawada K. (1993) J. Biol. Chem. 268, 7799-7808) showed that although MgPPi reduces the maximum number of trinitrophenylated RLR down to about 0.5 mol/mol of S1, this half-stoichiometric modification of RLR is not the result of any heterogeneity in the primary structure of S1. However, this result conflicts with a previous report in which the half-stoichiometric trinitrophenylation has been reported to be related to Pro/Ser microheterogeneity at the 78th residue position in the heavy chain of rabbit skeletal muscle myosin. To resolve the conflict, we isolated peptides containing both the 78th residue and RLR from the two different preparations of S1, one whose RLR was trinitrophenylated in the presence of MgPPi and the other whose RLR was not trinitrophenylated in the presence of MgPPi, and then we determined the amino acid sequences of the peptides. We found the same Pro/Ser microheterogeneity at the 78th position in the peptides from these S1s and thus concluded that this microheterogeneity has no correlation to the half-stoichiometric trinitrophenylation of RLR.

Highlights

Fl To whom correspondence should be addressed Dept. of Biology, Faculty of Science, Kyushu University, Fukuoka, Fukuoka 812, Japan
Our detailed kinetic study (Kcmatsuetal., 1993) confirmed the half-stoichiometric trinitrophenylation of RLR in the presence of MgPPi, the kineticstudy provided no evidencefor suchnonidentical functions of the two myosin heads as reported by Miyanishi et al (1979) but,instead, concluded that the half-stoichiometric trinitrophenylation is due to two different equimolar conformations of the myosin head in aslow equilibrium rather than due to the existenocf etwo different chemical structures
This paper will show that there is microheterogeneity of Pro/Ser at the 78th position in the heavy chain of rabbit skeletal muscle myosin, but that this microheterogeneity is not related to the half-stoichiometric trinitrophenylation of RLRinthepresence of MgPP;

Summary

Introduction

Fl To whom correspondence should be addressed Dept. of Biology, Faculty of Science, Kyushu University, Fukuoka, Fukuoka 812, Japan. They later isolated two different peptides containing RLRfrom the heavy chain of myosin and identified the 78th amino acid residue as Pro in one peptide and Ser in the other.

Results

Conclusion