3-METHYLHISTIDINE METABOLISM IN PROTEINS FROM CULTURED MAMMALIAN MUSCLE CELLS

Primary cultures of rat leg muscle cells were found capable of converting [l4C]histidine as well as [14C-methyl]-methionine into protein bound [14C]3-methylhistidine. The cultured cells were used to study the half-life of the labeled amino acids in acid-precipitable proteins undergoing turnover. The initial rates of turnover for histidine were estimated to be dependent not only on age of the muscle cell cultures, but also on types of proteins sampled from the cultures. Constant rates of decrease in radioactive 3-methylhistidine were noted in proteins from cells after 8 days in culture. These constant rates were obtained in preparations of total cell proteins, soluble proteins of cell sap, or preparations of actin and myosin sampled from these cultures. Turnover rates for preparations of actin and myosin from older cells of the same cultures were analogous. On the other hand, initial turnover rates for histidine and 3-methylhistidine isolated from actin and myosin preparations of young cultures were different. © 1969, American Chemical Society. All rights reserved.