title: Identification of cysteine-10 of protein S18 as part of the mRNA-binding site of Escherichia coli ribosomes by affinity-labeling studies with a chemically reactive A-U-G analog.
abstract: The reaction of a bromoacetamidophenyl derivative of the initiation codon A-U-G (A-U-G) with tight couples of Escherichia coli ribosomes leads to an exclusive crosslinking of label to protein S18. This crosslinking inhibits A-U-G-directed fMet-tRNAfMet binding into the puromycin-sensitive site of ribosomes and stimulates elongation-factor-dependent binding of Met-tRNAmMet. It is, therefore, concluded that protein S18 is located at or near the aminoacyl-tRNA binding site of E. coli ribosomes. Peptide as well as amino acid analysis shows that the reaction between A-U-G and ribosomes took place at cysteine-10 of protein S18. A-U-G could not be crosslinked to ribosomal proteins of the temperature-sensitive E. coli strain 258ts, where arginine-11 of protein S18 is replaced by a cysteine residue.
mesh_terms: D000345:Affinity Labels; D000596:Amino Acids / Q000032:analysis; D003062:Codon; D003545:Cysteine / Q000032:analysis*; D004926:Escherichia coli / Q000378:metabolism*; D009841:Oligonucleotides; D009843:Oligoribonucleotides; D012333:RNA, Messenger / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism
chemical_list: D000345:Affinity Labels; D000596:Amino Acids; D003062:Codon; D009841:Oligonucleotides; D009843:Oligoribonucleotides; D012333:RNA, Messenger; D012269:Ribosomal Proteins; D012343:RNA, Transfer; D003545:Cysteine