Deluene expression analysis of Streptococcus sobrinus UAB108

The mutans group cf streptococci possess several extracellular Sucrose-metabolizing enzymes and proteins that have been implicated as important factors in dental caries. Dextranase inhibitor (Dei) is one of them. A phenotypic dextranase-deficient i'Dex'; mutant (UAB108) of Streptococcus sobrinus UAB66 syntnesizes a huge amount of Dei. The dei gene from UAB108 was previously craned, expressed and sequenced. More evidence snows, this gene has its own promoter. DMA sequence and "rri-rn nyoricization analyses .vu h different probes from dei give icentioal transcnpts i lustrale that this gene has only one trarscr:ption initiation site and terminator as well. Primer extension ?.n:J Si mapping show tnat transcription starts from an adenosine \vr.v. r, 26 bp from the ATG start codon, ends at about 52 bp o'.vnnream ot cfe/gene. and gives an 1.1 kb transcript. Transcripts are p-oduced at rather consistent levels during logarithmic and ear y stationary growth stages. The half-life of dei mRNA at middle log phase is about 6.6 mm. The big difference of dei gene expression in UAB108 and UAB66 seems in transcription level. Some function related genes, such as dextranase (dex), giucosyltransferases (gtf-l. gtf-S), do not affect dei gene expression sigmfically m a series of co-transformation experiments in E. coli.