Question

EF-Tu...

A. binds GTP and delivers amino-acyl tRNAs to the A site of the ribosome

B. is hydrolyzed to allow release of initiation factors

C. binds GTP and allows ribosomal movement down the mRNA

D. allows base pairing between the mRNA and the 16s rRNA

Answer 1

A. Binds GTP and delivers amino-acyl tRNAs to the A- site of the ribosome.

In bacteria the entry of an amino acyl tRNA into the A-site is mediated by the elongation factor called EF-Tu. It remains associated with the ribosome only during tRNA entry and leaves the ribosome after placing amino acyl tRNA in the A- site. EF-Tu is a monomeric G protein which is active when bound to GTP. The binary complex of EF-Tu-GTP binds amino acyl tRNA to form a ternary complex. The ternary complex binds to the A-site of a ribosome whose P-site is occupied by peptidyl tRNA (initially the initiator tRNA). First the anticodon end binds to the A-site. The codon–anticodon recognition triggers a change in the conformation of ribosome. This stabilizes tRNA binding and causes EF-Tu to hydrolyze its bound GTP. Now EF-Tu-GDP complex is released from the ribosome. EF-Ts is a guanine nucleotide excange factor (GEF) that regenerates EF-TU -GTP by substituting GDP with GTP