Sequence analysis of the Streptococcus mutans fructosyltransferase gene and flanking regions

Abstract

The nucleotide sequence of the ftf gene from Streptococcus mutants GS-5 was determined. The deduced amino acid sequence indicates that the unprocessed fructosyltransferase gene product has a molecular weight of 87,600. A typical streptococcal signal sequence is present at the amino terminus of the protein. The processed enzyme is relatively hydrophilic and has a pI of 5.66. An inverted repeat structure was detected upstream from the ftf gene and may function in the regulation of fructosyltransferase expression. Sequencing of the regions flanking the gene revealed the presence of four other putative open reading frames (ORFs). Two of these, ORFs 2 and 3, appear to code for low-molecular-weight proteins containing amino acid sequences sharing homology with several gram-positive bacterial DNA-binding proteins. In addition, ORF 3 is transcribed from the ftf DNA coding strand. Partial sequencing of ORF 4 suggests that its gene product may be an extracellular protein.