Two GTPs are consumed on EF‐Tu per peptide bond in poly(Phe) synthesis, in spite of switching stoichiometry of the EF‐Tu·aminoacyl‐tRNA complex with temperature

Abstract

Recent observations indicate that the stoichiometry for the complex between EF-Tu • GTP and aminoacyl-tRNA (aatRNA) changes with temperature. At 37°C two EF-Tu.GTPs bind one aa-tRNA in an extended ternary complex, but at 0°C the complex has 1 : 1 stoichiometry. However, the present experiments show that there are two GTPs hydrolyzed on EF-Tu per peptide bond in poly(Phe) synthesis at 37°C as well as at 0 ° C. This indicates two different pathways for the enzymatic binding of aa-tRNA to the A-site on the ribosome.

Crystal Structure of the Ternary Complex of Phe-tRNA Phe , EF-Tu, and a GTP Analog

“…A 3'-oxidized tRNA in complex with E. coli EF-Tu-GTP (46) was shown to cross-link to Lys208 and Lys237 (Lys219 and Lys248 in T. quaticus), and a complex of two tRNAs per EF-Tu-GTP on the ribosome was suggested (47). These observations do not per tRNA in a quinternary ("pentameric") complex (48)(49)(50) is based on the observation that two GTPs are hydrolyzed for each elongation cycle. Although the exact interpretation has been questioned (51, 52) the consumption of two GTP equivalents was also reported from studies on an XTP binding EF-Tu mutant (53).…”