title: Complete sequence of the staphylococcal gene encoding protein A. A gene evolved through multiple duplications.
abstract: The gene coding for protein A from Staphylococcus aureus has been isolated by molecular cloning, and a subclone containing an 1.8-kilobase insert was found to give a functional protein A in Escherichia coli. The complete nucleotide sequence of the insert, including the structural gene and the 5' and 3' flanking sequences, has been determined. Starting from a TTG initiator codon, an open reading frame comprising 1527 nucleotides gives a preprotein of 509 amino acids and a predicted Mr = 58,703. The structural gene is flanked on both sides by palindromic structures followed by a stretch of T residues, suggesting transcriptional termination signals. Thus, it appears that protein A is translated from a monocistronic mRNA. The sequence reveals extensive internal homologies involving a 58-amino acid unit, responsible for IgG binding, repeated 5 times and an 8-amino acid unit, possibly responsible for binding to the cell wall of S. aureus, repeated 12 times. Comparisons between the repeated regions show a marked preference for silent mutations, indicating an evolutionary pressure to keep the amino acid sequence preserved. The structure of the gene also suggests how the gene has evolved.
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D003062:Codon; D004262:DNA Restriction Enzymes; D005796:Genes; D005798:Genes, Bacterial; D009690:Nucleic Acid Conformation; D009876:Operon; D010957:Plasmids; D013205:Staphylococcal Protein A / Q000235:genetics*; D013211:Staphylococcus aureus / Q000235:genetics*
chemical_list: D003062:Codon; D013205:Staphylococcal Protein A; D004262:DNA Restriction Enzymes