Publication: Comparison of the structure and function of polysomal and helical ribosomes from Entamoeba Invadens
Issued Date
1975-06-01
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ISSN
15408140
00219525
00219525
Other identifier(s)
2-s2.0-0016590662
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Mahidol University
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SCOPUS
Bibliographic Citation
Journal of Cell Biology. Vol.65, No.3 (1975), 540-548
Suggested Citation
Thanit Kusamrarn, Kamolwat Vinijchaikul, Gordon B. Bailey Comparison of the structure and function of polysomal and helical ribosomes from Entamoeba Invadens. Journal of Cell Biology. Vol.65, No.3 (1975), 540-548. doi:10.1083/jcb.65.3.540 Retrieved from: https://repository.li.mahidol.ac.th/handle/123456789/10739
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Title
Comparison of the structure and function of polysomal and helical ribosomes from Entamoeba Invadens
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Abstract
Some structural and functional properties of ribosomes from polysomes and from helix aggregates of Entamoeba invadens have been compared by sucrose gradient analysis and assays of in vitro protein synthesis. Actively growing trophozoites, lacking helices, presented normal polysome profiles in sucrose gradients. The single large ribosomal helix aggregate (chroma-toid body) of cysts disappeared as the cells were disrupted. Gradient profiles of cyst extracts contained predominantly large and small ribosome subunit peaks and no evidence of remaining helix fragments or mRNA-bound polysomes. Sequential profiles of trophozoites incubated with NaF or cycloheximide (which both stimulate ribosome aggregation, but at different rates) showed that polysome breakdown occurred before aggregates appeared and, again, that helices broke down to subunits in vitro. Radioactive ribosomes synthesized during vegetative growth were collected into helices during encystation. Subunits of these ribosomes cosedimented with comparable particles isolated from trophozoites. Ribosomes from both trophozoites and cysts were active in cell-free protein synthesis, although activity in cyst extracts required the addition of trophozoite-soluble fraction. It was concluded that ribosomes from polysomes and helices in E. invadens were probably identical and that the ability to form helices was an intrinsic property of mature mRNA-free ribosomes of this organism. © 1975, Rockefeller University Press., All rights reserved.