Structural Basis For Inhibition Of Ribosome Translocation By Neomycin

During the protein translation process,the process of amino acids based on the m RNA template sequence to the extension peptide chain is called the translation elongation,which is the core step of protein translation.Ribosome translocation as a complex key step in the protein translation,it enables t RNA and m RNA to enter and leave in order on the ribosome,which is the most basic sub-step in the translation elongation.Previous studies on bacterial translation showed that it was mainly divided into two steps,firstly the 3 ’end of t RNA at the A site moves into the P site under the movements of 50 S,while the anticodon stem loop(ASL)is still at the A site of 30S;the second step in the catalysis of the translation factor EF-G and GTP,the ASL of t RNA and m RNA have completely left A site with 30 S movement,next round of peptide chains could be extended in the empty A site.Previous biological chemistry studies have proved translocation could be blocked by aminoglycoside antibiotic neomycin,but the molecular mechanisms in which neomycin inhibits EF-G catalyzed translocation is not fully understood.Therefore,we successfully solved the cryo-EM structure of neomycin bound with ribosome complex and the crystal structures of neomycin inhibiting EF-G catalyzed translocation complexes,and identified four bound neomycin molecules(Neo1-4),all of which bind to intersubunit bridges,as well as a neomycin molecules(Neo1)bound with classical ribosome.Neo2 and Neo3 bound between H69 and H70(H represents the second structure helix of 23 r RNA),restricting the movement of H69 and stabilizing bridges B2 a and B2 d in a rotated conformation.Neo4 bound to H67 and H71,also stabilizing intersubunit bridge B2 c in a rotated conformation,which may be to block translocation by stabilizing the ribosome chimeric-hybrid state,providing a new insight for neomycin inhibiting EF-G catalyzed translocation.