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[摘要]：Protein L7/L12 of the bacterial ribosome plays an important role in activating the GTP hydrolytic activity of elongation factor G (EF-G), which promotes ribosomal translocation during protein synthesis. Previously, we cross-linked L7/L12 from two residues (209 and 231) flanking alpha-helixA(G ') in theG ' subdomain of Escherichia coli EF-G. Here we report kinetic studies on the functional effects of mutating three neighboring glutamic acid residues ( 224, 228, and 231) to lysine, either singly or in combination. Two single mutations ( E224K and E228K), both within helix A(G '), caused large defects in GTP hydrolysis and smaller defects in ribosomal translocation. Removal of L7/L12 from the ribosome strongly reduced the activities of wild type EF-G but had no effect on the activities of the E224K and E228K mutants. Together, these results provide evidence for functionally important interactions between helix A(G ') of EF-G and L7/L12 of the ribosome. |
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