The structural basis for the resistance of Escherichia coli formylmethionyl transfer ribonucleic acid to cleavage by Escherichia coli peptidyl transfer ribonucleic acid hydrolase.
Escherichia coli formylmethionly-tRNA-tMet is unique among N-acylaminoacyl-tRNAs in its resistance to cleavage by peptidyl-tRNA hydrolase. Chemical modification of tRNA-fMet with sodium bisulfite converts fMet-tRNA-fMet into a good substrate for the hydrolase. The products of the enzymatic cleavage are free tRNA-fMet and formylmethionine. Bisulfite treatment produces cytidine to uridine base changes at several sites in the tRNA structure. One of these modifications results in formation of a new hydrogen-bonded base pair at the end of the acceptor stem of tRNA-fMet. We have shown that this modification is responsible for the observed change in biological activity. Enzymatic cleavage appears to be facilitated by the presence of a 5-terminal phosphate at the end of a fully base-paired acceptor stem, because removal of the 5-phosphate group from N-acetylphenylalanyl-tRNA-Phe or bisulfite-modified fMet-tRNA-FMet reduced the rate of hydrolysis of these substrates. The unpaired base at the 5 terminus of unmodified fMet-tRNA-fMet appears to reduce susceptibility of the tRNA to hydrolytic attack both by positioning the 5-phosphate in an unfavorable orientation and by directly interfering with enzymatic binding. The unusual structure of the acceptor stem of this E. coli tRNA thus plays a critical role in maintaining the viability of the organism by preventing enzymatic cleavage of the fMet group from the bacterial initiator tRNA.
D000604:Amino Acyl-tRNA Synthetases; D001483:Base Sequence; D001665:Binding Sites; D002845:Chromatography; D004926:Escherichia coli / Q000201:enzymology*; D006867:Hydrolases / Q000302:isolation & purification; D008715:Methionine / Q000031:analogs & derivatives; D009690:Nucleic Acid Conformation; D010455:Peptides; D010649:Phenylalanine / Q000031:analogs & derivatives; D012329:RNA, Bacterial; D012343:RNA, Transfer; D013447:Sulfites
D010455:Peptides; D012329:RNA, Bacterial; D013447:Sulfites; D010649:Phenylalanine; D012343:RNA, Transfer; D008715:Methionine; D006867:Hydrolases; D000604:Amino Acyl-tRNA Synthetases