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Biochemical Studies of Bacterial Sporulation and Germination

XI. PROTEIN-SYNTHESIZING SYSTEMS FROM VEGETATIVE CELLS AND SPORES OF BACILLUS MEGATERIUM

From the ¹ From the Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305

The protein-synthesizing systems isolated from vegetative cells and spores of Bacillus megaterium were compared. The capacity for polyphenylalanine synthesis, directed by polyuridylate, was essentially the same for both systems under optimal conditions and amounted to approximately 8 mµmoles of phenylalanine incorporated in 30 min per mg of ribosomal protein. Amino acid incorporation dependent on endogenous messenger RNA in the spore system was 20 to 30% of that obtained with endogenous vegetative cell messenger. The requirements of each system for Mg⁺⁺, NH₄⁺, and spermidine were similar, as were the pH optima. Some differences between the two systems were observed in their dependence on ribosomes, supernatant fractions, transfer RNA, and polyuridylate. Transfer RNA from vegetative cells and spores had similar acceptor activities for several amino acids; however, methionine was esterified to spore transfer RNA at 3 times the level seen with vegetative cell material.

Spore ribosomes contained an inhibitor of amino acid incorporation. Nuclease activity, assayed by hydrolysis of polyuridylate, was greater in spore ribosomes and supernatant fractions than in their vegetative cell counterparts. These results suggest that the capacity for protein synthesis is identical in spores and vegetative cells, and that the deficiencies in the spore system observed under certain conditions may be attributable to the presence of nuclease.

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