Bacterial hydrolysis of protein and methylated protein and its implications for studies of protein degradation in aquatic systems.

Ribulose 1,5-bisphosphate carboxylase was radiolabelled by in vitro translation, resulting in uniformly labelled ribulose 1,5-bisphosphate carboxylase, and also by reductive methylation. We investigated the degradation of the two forms of radiolabelled protein by natural bacterial populations. Although total hydrolysis of uniformly labelled protein and methylated protein was nearly equal, percent assimilation, respiration, and release as low-molecular-weight material were different. Radioactivity from uniformly labelled protein was approximately equally assimilated into cells, respired as H(2)O, and released as low-molecular-weight material, but radioactivity from the methylated protein was nearly all released as low-molecular-weight material, and little was assimilated or respired.