The glucosyltransferase gene, , is positively regulated by the upstream determinant . In the present study, two ORFs, transcribed on the opposite DNA strand, were identified immediately downstream of . The first, designated , shares a convergent putative transcriptional terminator with , and encodes a predicted 46 kDa transmembrane protein similar to the TrsA involved in polysaccharide biosynthesis. Insertional inactivation of resulted in only ∼∼60% of the parental level of glucosyltransferase activity. The 870 bp gene 5′ to is similar to the regulatory determinant. Designated , this -like determinant downstream of encodes a putative 336 kDa cytoplasmic protein. Despite their sequence similarity, the functions of and appear specific. Strains in which was insertionally inactivated and strains containing plasmid-borne had parental levels of glucosyltransferase activity. Northern blot hybridization analyses showed ∼13 kb -specific and ∼10 kb -specific mRNA transcripts associated with this region; no polycistronic transcript was observed. Although like gene products have been demonstrated to function as positive transcriptional regulators of adjacent genes in several streptococcal species, Northern blot analysis suggested that did not influence the transcription of or the divergent downstream -like determinant under the conditions in the present study. Comparison of this chromosome region to other streptococcal genomes, which do not contain the /-flanked region involved in glucan synthesis, raised intriguing possibilities about the origins of this chromosomal region, and also suggested that might regulate a distally located gene.


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