Genetic transformation in Streptococcus pneumoniae: nucleotide sequence analysis shows comA, a gene required for competence induction, to be a member of the bacterial ATP-dependent transport protein family

The complete nucleotide sequence of comA, a gene required for induction of competence for genetic transformation in Streptococcus pneumoniae, was determined by using plasmid DNA templates and synthetic oligonucleotide primers. The sequence contained a single large open reading frame, ORF1, of 2,151 bp. ORF1 was included within the comAB locus previously mapped genetically and accounted for 50% of its extent. The predicted molecular weight of the largest polypeptide encoded within ORF1, 80,290, coincided with that measured previously (77,000) for the product of in vitro transcription-translation of the cloned comA locus. A Shine-Dalgarno sequence (AAAGGAG, delta G = -14 kcal) lay immediately upstream of ORF1. A sequence (TTtAat-17 bp-TAaAAT) similar to the Escherichia coli sigma 70 promoter consensus was located 410 bp upstream of ORF1. The deduced protein sequence of ComA showed a very strong similarity to the E. coli hemolysin secretion protein, HlyB, and strong similarities to other members of the family of ATP-dependent transport proteins, including the mammalian multidrug resistance P-glycoprotein. These similarities suggest that ComA functions in the transport of some molecule, possibly pneumococcal competence factor itself.