Nucleotide sequence of pilA, the gene encoding the structural component of type 1 pili in Escherichia coli

The pilA gene of Escherichia coli J96 encoding pilin, the structural component of type 1 pili, was sequenced and found to specify a polypeptide 159 amino acids long preceded by a 23-amino-acid signal peptide. As determined from the DNA sequence, the mature peptide lacked tryptophane and methionine, two amino acids previously shown to be lacking in type 1 pili from E. coli. Also, the amino-terminal sequence of amino acids inferred from the DNA sequence corresponded to earlier 20-amino-acid amino-terminal sequences determined by protein sequencing. In addition, piliation was abolished after a mutation was introduced into the pilA coding region in vitro. A possible site for initiation of transcription and a possible site encoding translation initiation were suggested 85 and 7 base pairs, respectively, from the pilA start codon. There appeared to be scant DNA sequence homology and scant amino acid sequence homology between type 1 pilin and other pilin species isolated from uropathogenic and enteropathogenic E. coli.