Complex formation of the elongation factor Tu from Pseudomonas aeruginosa with nucleoside diphosphate kinase modulates ribosomal GTP synthesis and peptide chain elongation.
The elongation factor Tu (EF-Tu) from Pseudomonas aeruginosa was purified as a 45-kDa polypeptide that forms a complex with both the 12- and 16-kDa forms of nucleoside-diphosphate kinase (Ndk) and predominantly synthesizes GTP. 70 S ribosomes of P. aeruginosa predominantly synthesize GTP, which is inhibited in presence of anti-Ndk antibodies. Anti-EF-Tu antibodies change the specificity of ribosomal GTP synthesis to all nucleoside triphosphate synthesis. Ndk has been shown to be a part of 30 S ribosomes, whereas EF-Tu is found to be associated with the 50 S ribosomal subunit. These data indicate that GTP synthesis in the ribosome is modulated both by Ndk and by EF-Tu. Peptide chain elongation as measured by polymerization of Phe-tRNA on a poly(U) template in presence of GDP can be inhibited by anti-Ndk antibodies and restored by the addition of GTP. Anti-EF-Tu antibodies similarly inhibit peptide chain elongation by P. aeruginosa ribosomes in the in vitro translation assay; however, this inhibition cannot be overcome by adding back GTP. Because the purified EF-Tu.16-kDa Ndk complex predominantly synthesizes GTP, it seems likely that this complex is a significant source of GTP for translational elongation in protein biosynthesis.
Mukhopadhyay
S
S
Department of Microbiology and Immunology, University of Illinois College of Medicine, Chicago, Illinois 60612-7344, USA.
Shankar
S
S
Walden
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W
Chakrabarty
A M
AM
D000906:Antibodies / Q000378:metabolism; D002499:Centrifugation, Density Gradient; D002689:Chlamydia; D004926:Escherichia coli; D006160:Guanosine Triphosphate / Q000096:biosynthesis*; D046911:Macromolecular Substances; D008970:Molecular Weight; D009701:Nucleoside-Diphosphate Kinase / Q000378:metabolism*; D010441:Peptide Chain Elongation, Translational; D010444:Peptide Elongation Factor Tu / Q000378:metabolism*; D011550:Pseudomonas aeruginosa; D012270:Ribosomes / Q000378:metabolism*
D000906:Antibodies; D046911:Macromolecular Substances; D006160:Guanosine Triphosphate; D009701:Nucleoside-Diphosphate Kinase; D010444:Peptide Elongation Factor Tu