ISSN:
0021-9541
Keywords:
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Medicine
Notes:
Partially purified preparations of two protein factors, one of which is stable at 50°C (FIs) and the other unstable at 50°C (FIu), are required for the GTP-dependent, mRNA-directed binding of aminoacyl-tRNA to ribosomes, as well as for polypeptide synthesis in the presence of a third factor, FII. Both FIs and FIu are required for maximal interaction with GTP to form a GTP•protein complex that subsequently interacts with aminoacyl-tRNA, but not with deacylated tRNA or with N-(substituted)-aminoacyl-tRNA, to form an aminoacyl-tRNA•GTP•protein complex. A mixture of FIs and FIu also interacts with GDP to form a GDP•protein complex; however, no subsequent interaction with aminoacyl-tRNA is observed. In addition to aminoacyl-tRNA and GTP, Mg2+ and NH4+ are required for the formation of the aminoacyl-tRNA•GTP•protein complex. Although both protein factors, FIs and FIu, are required for the formation of this complex, only the heat-labile protein, FIu, is a component of the complex. Very little dissociation of the GTP moiety of the complex occurs in the presence of Mg2+, and no detectable exchange is observed with GTP, GDP, or Pi. In contrast, appreciable dissociation of the aminoacyl-tRNA from the GTP•protein occurs even in the presence of Mg2+, and exchange with other aminoacyl-tRNA's can be readily demonstrated. In the absence of Mg2+, complete dissociation of both the GTP and the aminoacyl-tRNA from the protein occurs. Evidence has been obtained to demonstrate that the aminoacyl-tRNA•GTP•protein complex is an intermediate in the GTP-dependent binding of aminoacyl-tRNA to ribosomes. The binding of the aminoacyl-tRNA to the ribosome occurs with the concomitant formation of Pi and a GDP • protein complex. Incorporation of the bound aminoacyl-tRNA into polypeptide requires additional GTP and the third transfer factor, FII.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jcp.1040740409
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