Question

a) Describe how EF-tu contributes to the fidelity of translation? In your answer include the role of GTP binding and hydrolysis. b)Describe the 2 process that (besides EF-Tu) contributes to the fidelity of translation elongation and in your answer discuss which very reliable enzyme with proof-reading capacity mediates this step.

ef-tu (elongation factor thermo unstable) catalyzes binding of tRNA to ribosomes. it is a g protein

Answer 1

Explanation for the Figure.

1. Ternary complex (EF-Tu-GTP-aa tRNA) binds at A/T site of ribosome.

2. Binding leads to the activation of GTPase activity of ribosome. This leads to hydrolysis of GTP and results in formation of EF-Tu-GDP-aa tRNA and ribosome complex.

3. In step 3, perfectly match aa tRNA will release EF-Tu-GDP and forms aa tRNA and ribosome complex.

4. EF-Ts will replace GDP with GTP

5. Formation of active ternary complex for the next round of cycle.

Proofreading by EF-Tu is explained below

1. Matching anticodon of t-RNA with m-RNA decide the selection of ternary complex at A/T site. If matching is perfect then ribosome activates GTPase activity of EF-Tu and hydrolysis of GTP takes place (Figure, proof reading 1). In case of mismatch, GTPase activity will not activate and results in the dissociation of ternary complex.

2. Even though of codon-anticodon matching at first step, second proof reading activity of the EF-Tu gives fidelity to the translation. EF-Tu induces delay in the formation of active ternary complex for the next cycle. This delay will give more time to aa tRNA for adjustment at A site of ribosome and provide second check (Figure, proof reading 2) in the process of accommodation.