Effect of the integrity of the myofibrillar structure on the tryptic accessibility of a hinge region of the myosin rod

Abstract

Limited proteolysis has been used to study the influence of actin, in the absence ar presence of regulatory proteins of the thin filament (tropomyosin and troponin), as well as that of the myofibrillar structure on the tryptic cleavage of the heavy meromyosin (HMM)/l~ght meromyosin (LMM) hinge region in myosin heavy chain. Cleavage at the HMM~LMM hinge is dmost absent in myofibrib, whereas this hinge is accessible to tryptic digestion in actomyosin, in native thin @aments attached to myosin and in myosin heavy chain aione, This observation indicates that it is the myofibriltar structure which profoundly affects the tryptic accessibility of this specific hinge region of myosin. This provides a good example of the manner by which a highly organized supramolecular structure might affect t.he chemical properties of a specific site in a macromolecule. Myosin hinge region Tryptic proteolysis

Thick and Thin Filament Gene Mutations in Striated Muscle Diseases

“…The MyHC can be cleaved by proteolytic enzymes into two subfragments, heavy meromyosin (HMM) and light meromyosin (LMM) [ 12 , 13 ]. The HMM contains the head region, termed subfragment 1 (S1), and a portion of the coiled-coil-forming sequence referred to as subfragment 2 (S2) which connects the myosin heads to the thick filament.…”