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The Incorporation of Leucine-C14 into Microsomal Particles and other Subcellular Components of the Pea Epicotyl

Ts'o, Paul and Sato, Clifford S. (1959) The Incorporation of Leucine-C14 into Microsomal Particles and other Subcellular Components of the Pea Epicotyl. Journal of Cell Biology, 5 (1). pp. 59-68. ISSN 0021-9525. PMCID PMC2224622. doi:10.1083/jcb.5.1.59.

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Incorporation of leucine-C14 into subcellular fractions of the apical section of pea seedlings has been studied as a function of the length of incubation. The specific activity of the microsomes was higher than that of the supernatant for short but not for long incubations, in agreement with observations on other systems. In this developing tissue the nuclei and especially the mitochondria appear to incorporate amino acid very rapidly. An insoluble fraction of the microsome pellet, which is presumably a liponucleoprotein complex, was found to possess, after 1 hour of incubation, a specific activity much greater than that of the purified microsomal particles or the supernatant fraction. Ninety-eight per cent of the leucine-C14 in the purified microsomal particles has been shown to possess bound amino groups, presumably in peptide linkages, by the DNP-end group method. These particles liberate but little peptide or protein of very high specific activity when they are destroyed by removal of Mg or by hydrolysis of RNA. Microsomal particles were fractionated into an RNA fraction and five protein fractions by means of density gradient centrifugation. By this method 95 per cent of the RNA can be separated from 90 per cent of the protein of the particle. Furthermore, the RNA fraction has been shown to contain very little protein of high specific activity. A particular protein fraction which contains the remaining 5 per cent of the RNA, possessed after 1 hour of incubation a specific activity 2 to 9 times higher than the protein of the other fractions.

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Additional Information:© 1959 by Rockefeller University Press (Received for publication, July 27, 1958) We wish to thank Prof. J. Bonner for his active support and helpful suggestions in this work, and Dr. J. Vinograd for his advice concerning the sedimentation in density gradients. The capable assistance of Mrs. J. R. Pilcher and Mrs. Christine Ziegler is also gratefully acknowledged. Report of work supported in part by grants No. RG-3977 and No. RG-5143 from the National Institutes of Health, United States Public Health Service.
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PubMed Central ID:PMC2224622
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ID Code:4410
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Deposited On:22 Aug 2006
Last Modified:08 Nov 2021 20:17

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