Age-related changes in turnover and concentration of a subset of thorax polypeptides from Drosophila melanogaster.

Six polypeptides from Drosophila melanogaster were analyzed by two-dimensional polyacrylamide gel electrophoresis for age-related changes in protein turnover and protein concentration. The protein samples, from thoraces of 6 day (young), 26 day (middle) and 45 day (old) flies, were compared using autoradiography for [35S]methionine labeled proteins and silverstaining for unlabeled preparations. The combination of these two techniques has permitted determination of the relative turnover rate as well as the steady-state concentration of these proteins as a function of age. The autoradiographs reveal that all of the analyzed proteins decrease in turnover rate whereas the absolute protein concentrations, as determined from the silverstained gels, show a decrease for three proteins, no change for two, and an increase in one protein with age. These findings show a remarkable quantitative heterogeneity of ageing changes in proteins, but absence of alterations in the fidelity of the translation of these polypeptides.