The Function Of Ribosome Large Protein L11 Loop62 During Regulating Protein Translation

During the process of protein translation, the energy is generated in the process of GTP hydrolysis into GDP and release inorganic Pi. There is a GTPase-associated center ( GAC) in the ribosome. GAC is responsible for stimulating the hydrolysis activity of GTPase participating in the translation. It consists of three important parts: the sarcin-ricin loop (SRL) of 23S rRNA, the protein L10 and the stalk of L7/L12 and the stalk base (SB) -L11 and its binding site on helix 43/44 (H43/H44) of the 23S rRNA. In the prokaryotes, the protein L11 and L7/L12 are highly conserved.L7/L12 stalk is located in the large subunit of ribosome and it consists of L10, L11 and multiple copy of L7/L12. In E.coli, there is four copies of L7/L12. L7/L12-NTD binds with the 23S rRNA, and interacts with L10. L7/L12-CTD stretches outside of the ribosome to recruit trGTPase.L11 consists of NTD and CTD, and L11-CTD binds with the H43/H44 of 23S rRNA. There is a flexible loop between the CTD and NTD. The structure of L11-NTD is loose relatively, and swinging in the ribosome. trGTPase can change the conformation of L11 while it binding with ribosome, and it is important for connecting L7/L12. L7/L12 can stimulate the activity of GTPase of translation factors. The interaction with L7/L12 can be controlled by the conformational change of L11 like a molecular switch regulating the function of trGTPase.In the article, we focus on the effect of the protein L11-NTD loop62 in the GTP hydrolysis and the translation of ribosome. The loop62 in L11-NTD is a very short and flexible loop and its function is very important. It is close to L12-CTD, and it is the interaction site between L11 and L12 from X-ray. Loop62 consists of four animo acids: Tyr, Ala, Asp and Arg. They are highly conserved, especially Asp. We do some mutants: Tyr62Ala, Asp64Ala and Arg65Ala, and find the activity of GTP hydrolysis is reduced. The ability of in vitro translation is reduced, too. These explain the mutants of loop62 affect the function of ribosome and loop62 has a certain role in regulating the GTP hydrolysis of ribosome dependence and protein translation.