Incorporation of Amino Acids into the Proteins of Micrococcus Iysodeikticus

Citation

Lester, Robert Leonard (1956) Incorporation of Amino Acids into the Proteins of Micrococcus Iysodeikticus. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/V4K5-ZD08. https://resolver.caltech.edu/CaltechETD:etd-03262004-141353

Abstract

Lysis of Micrococcus lysodeikticus cells with lysozyme in the presence of high concentrations of sucrose has yielded a particulate system, distinct from intact cells, that carries out the incorporation of amino acids into protein. All seven amino acids which have been tested have been incorporated. The system was sedimentable, had a high endogenous respiration, and required the continued presence of high sucrose or KCl concentrations for activity. The importance of oxidative reactions for incorporation was indicated since anaerobiosis and 2,4-dinitrophenol treatment inhibited incorporation. Ribonuclease treatment diminished incorporation; desoxyribonuclease treatment accelerated incorporation. The activity of the particulate system was inversely related to the concentration at which these particles were assayed. Stimulation of incorporation was observed upon addition of unlabeled amino acids implying a net synthesis of protein molecules under these conditions. From data obtained on the composition of the free amino acid pool and the rates of amino acid incorporation it was concluded that in the absence of added amino acids, amino acid incorporation occurred either via an exchange reaction or that it reflected synthesis of new protein molecules with concomitant breakdown of pre-existing protein to amino acids. It was shown that radioactive protein isolated after incubation with radioactive leucine, contained leucine as its sole radioactive constituent. The conversion of leucine to alpha-ketoisocaproic acid was also shown.

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