Open AccessComparison of the tryptic digestion pattern of subfragments 1 from V1 and V3 rat cardiac isomyosins
Author(s) -
LOMPRÉ AnneMarie,
HAN KiaKi,
BOUVERET Pierre,
RICHARD Claude,
SCHWARTZ Ketty
Publication year - 1984
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1984.tb08028.x
Subject(s) - proteolysis , trypsin , peptide , myosin , digestion (alchemy) , chemistry , biochemistry , nucleotide , cleavage (geology) , chymotrypsin , cardiac muscle , enzyme , microbiology and biotechnology , biology , chromatography , endocrinology , gene , paleontology , fracture (geology)
The limited tryptic digestion patterns of the chymotryptic subfragment 1 (S1) of the two rat ventricular isomyosins V1 and V3, were compared under several conditions. Pure S1V1 was obtained from 3‐week‐old rats and pure S1V3 from adult rats 6 weeks after hypophysectomy. To localize the sites of trypsin susceptibility and to determine the distribution of the peptides along the S1 molecule, we used, as a probe, antibodies raised against a pig cardiac 29‐kDa peptide. We demonstrate that this peptide contains the N ‐acetyl group located on the N‐terminal part of the cardiac myosin molecule. In S1V1 we observed two major sites of proteolysis, independently of the digestion conditions: they are located at 27kDa and 80kDa from the N terminus as in skeletal muscle S1. S1V3 appears much more sensitive to the proteolysis conditions: at least two additional sites of cleavage are present in the 50‐kDa peptide when digested at pH 8.0. Decrease in the pH from 8.0 to 7.0 or the presence of Mg‐ATP have no effect on the digestion of S1V1 while these ambient factors protect the 50‐kDa peptide of S1V3 from breakdown. We conclude that the 50‐kDa peptide is a variable portion of the myosin molecule, the conformation of which is sensitive to ambient factors such as the pH or the presence of nucleotides.