Nucleotide sequence analysis of a type 1 fimbrial gene of Streptococcus sanguis FW213

Abstract

A structural gene for type 1 fimbriae of Streptococcus sanguis FW213 was located within a 6-kilobase fragment cloned in Escherichia coli. A 1.6-kilobase internal fragment contains an open reading frame of 927 bases coding for an immunoreactive peptide of 34,349 daltons, which corresponds in size with an observed cytoplasmic form of fimbrial peptide (P. M. Fives-Taylor, F. L. Macrina, T. J. Pritchard, and S. J. Peene, Infect. Immun. 55:123-128, 1987). Disruption of the reading frame by insertional mutagenesis results in loss of immunoreactivity. Consensus sequences for initiation of transcription and translation were identified 5' to the coding region. Transcription terminator-like sequences were found downstream of the coding region. The deduced amino acid sequence of the cloned fimbrial peptide shows a strongly hydrophobic signal sequence at the amino terminus. The carboxyl-terminal region does not include a hydrophobic membrane anchor sequence such as has been reported for other gram-positive surface structures. A hydrophobic region of 12 to 14 amino acids downstream from the putative signal sequence cleavage site exhibits homology with the Streptococcus pyogenes type 6 M protein repetitive region A (S. K. Hollingshead, V. A. Fischetti, and J. R. Scott, J. Biol. Chem., 261:1677-1686, 1986). Functional homology at the level of protein secondary structure with Actinomyces viscosus T14V type 1 fimbriae (M. K. Yeung, B. M. Chassy, and J. O. Cisar, J. Bacteriol., 169:1678-1683, 1987) is proposed.