Analysis of the altered mRNA stability (ams) gene from Escherichia coli. Nucleotide sequence, transcriptional analysis, and homology of its product to MRP3, a mitochondrial ribosomal protein from Neurospora crassa

The product of the altered mRNA stability (ams) gene of Escherichia coli is involved in decay of mRNA. The complete nucleotide sequence of a 4-kilobase BamHI restriction fragment containing the ams coding sequence was determined. Transcription of the ams gene was analyzed by high resolution S1 mapping. A promoter was found with a homology score of 58% 361 nucleotides upstream from the start codon of ams. The ams structural gene consists of an open reading frame of 2,445 nucleotides. The protein predicted from this open reading frame has a molecular mass of 91,327 Da, which is significantly smaller than that determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. Confirmation of the ams coding sequence was obtained by comparing the predicted amino acid sequence with that derived by amino-terminal analysis of gel-purified Ams protein. The predicted protein sequence of the ams gene was screened against translations of the GenBank DNA sequence data base. A homology of 18% over a region of 315 amino acids of the carboxyl terminus of the Ams product was found to MRP3, a mitochondrial ribosomal protein from Neurospora crassa. A smaller region of homology (29% in 86 residues) was found to the human U1 small nuclear ribonucleoparticle 70,000-Da protein.