The ability of chloroplasts isolated from Acetabulana mediterranea to synthesize the protein amino acids has been investigated. When this chloroplast isolate was presented with 14CO2 for periods of 6–8 hr, tracer was found in essentially all amino acid species of their hydrolyzed protein Phenylalanine labeling was not detected, probably due to technical problems, and hydroxyproline labeling was not tested for The incorporation of 14CO2 into the amino acids is driven by light and, as indicated by the amount of radioactivity lost during ninhydrin decarboxylation on the chromatograms, the amino acids appear to be uniformly labeled. The amino acid labeling pattern of the isolate is similar to that found in plastids labeled with 14CO2 in vivo. The chloroplast isolate did not utilize detectable amounts of externally supplied amino acids in light or, with added adenosine triphosphate (ATP), in darkness. It is concluded that these chloroplasts are a tight cytoplasmic compartment that is independent in supplying the amino acids used for its own protein synthesis. These results are discussed in terms of the role of contaminants in the observed synthesis, the "normalcy" of Acetabularia chloroplasts, the synthetic pathways for amino acids in plastids, and the implications of these observations for cell compartmentation and chloroplast autonomy.
Article|
August 01 1972
BIOSYNTHESIS IN ISOLATED ACETABULARIA CHLOROPLASTS : I. Protein Amino Acids
David C. Shephard
,
David C. Shephard
From the Department of Anatomy, Case Western Reserve University, Cleveland, Ohio 44106
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Wendy B. Levin
Wendy B. Levin
From the Department of Anatomy, Case Western Reserve University, Cleveland, Ohio 44106
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David C. Shephard
From the Department of Anatomy, Case Western Reserve University, Cleveland, Ohio 44106
Wendy B. Levin
From the Department of Anatomy, Case Western Reserve University, Cleveland, Ohio 44106
Received:
July 01 1971
Revision Received:
April 17 1972
Online Issn: 1540-8140
Print Issn: 0021-9525
Copyright © 1972 by The Rockefeller University Press
1972
J Cell Biol (1972) 54 (2): 279–294.
Article history
Received:
July 01 1971
Revision Received:
April 17 1972
Citation
David C. Shephard, Wendy B. Levin; BIOSYNTHESIS IN ISOLATED ACETABULARIA CHLOROPLASTS : I. Protein Amino Acids . J Cell Biol 1 August 1972; 54 (2): 279–294. doi: https://doi.org/10.1083/jcb.54.2.279
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