THE CELL-BOUND FRUCTOSYLTRANSFERASE OF STREPTOCOCCUS-SALIVARIUS - THECARBOXYL-TERMINUS SPECIFIES ATTACHMENT IN A STREPTOCOCCUS-GORDONII MODEL SYSTEM

The ftf gene, coding for the cell-bound beta-D-fructosyltransferase (F TF) of Streptococcus salivarius ATCC 25975, has been analyzed, and its deduced amino acid sequence has been compared with that of the secret ed FTF of Streptococcus mutans and the levansucrases (SacBs) of Bacill us species. A unique proline-rich region detected at the C terminus of the FTF of S. salivarius preceded a hydrophobic terminal domain. This proline-rich region was shown to possess strong homology to the produ ct of the prgC gene from pCF10 in Enterococcus faecalis, which encodes a pheromone-responsive protein of unknown function, as well as homolo gy to the human proline-rich salivary protein PRP4. A series of 3'-OH deletions of the S. salivarius ftf gene expressed in Streptococcus gor donii Challis LGR2 showed that the C terminus was required for cell su rface attachment in this heterologous organism, as only the complete g ene product was cell bound. This cell-bound activity was released in t he presence of sucrose, suggesting that the mode of attachment and rel ease of the S. salivarius FTF in S. gordonii was similar to that in it s native host.