Sequence analysis of the wall‐associated protein precursor of Streptococcus mutans antigen A

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Abstract
The nucleotide sequence has been determined for the Streptococcus mutans wall‐associated protein A (wapA) gene from serotype c strains Ingbritt and GS5. The nucleotide sequence for each wapA gene was virtually identical, although the gene from strain GS5 contained a 24 base pair deletion. A 29 amino acid signal peptide was specified by each wapA gene with a mature protein of 424 amino acids (Mr, 45276) for strain Ingbritt and 416 amino acids (Mr, 44846) for strain GS5. In the C‐terminal region of the wall‐associated protein A, considerable sequence similarity was found with the membrane anchor region of proteins from other Gram‐positive organisms such as the group A streptococcal M protein and the group G streptococcal IgG binding protein. Adjacent to the proposed membrane anchor is a highly hydrophilic region which may span the cell wall; both sequence data and experimental evidence indicate the existence of a region immediately outside the wall at which proteolytic cleavage occurs to release antigen A of Mr 29000 into the culture supernatant. Thus, the wall‐associated protein A is a precursor of the 29000 Mr antigen A.