title: Guanosine 5'-O-(3-thiotriphosphate) as an analog of GTP in protein biosynthesis. The effects of temperature and polycations on the accuracy of initial recognition of aminoacyl-tRNA ternary complexes by ribosomes.
abstract: Guanosine 5'-O-(3-thio)triphosphate (GTP gamma S) is a good analog of GTP in the reactions leading to the formation of a peptide bond in protein biosynthesis. It forms binary and ternary complexes with elongation factor Tu (EF-Tu), and with EF-Tu and aminoacyl-tRNA (aa-tRNA). In addition, it stimulates aa-tRNA binding to ribosomes. Although GTP gamma S hydrolysis is more than three orders of magnitude slower than GTP hydrolysis, both reactions are dependent on the formation of a noncovalent complex (RS X TC) between mRNA-programmed ribosomes and ternary complex, and the complexes resulting from that hydrolysis are intermediates in peptide formation. The rate of dissociation of the ribosome X EF-Tu X GTP gamma S X aa-tRNA complex was determined from the rate of labeled peptide formation in the presence of an unlabeled ternary complex chase. This rate (2.2 X 10(-3) s-1) is similar to that determined previously (Thompson, R.C., and Karim, A.M. (1982) Proc. Natl. Acad. Sci. U.S.A. 79, 4922-4926) from the progress of GTP gamma S hydrolysis. The effects of temperature and polycation concentration on this rate constant and that for GTP gamma S hydrolysis are reported. The rate constants measured are consistent with a kinetic rather than thermodynamic limit on the accuracy of the aa-tRNA selection in vivo.
mesh_terms: D004926:Escherichia coli; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D010444:Peptide Elongation Factor Tu / Q000378:metabolism; D011072:Poly U / Q000378:metabolism; D014176:Protein Biosynthesis; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism*; D013095:Spermidine / Q000494:pharmacology; D013696:Temperature; D013873:Thionucleotides / Q000378:metabolism*
chemical_list: D012346:RNA, Transfer, Amino Acyl; D013873:Thionucleotides; D011072:Poly U; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D010444:Peptide Elongation Factor Tu; D008274:Magnesium; D013095:Spermidine