Cl. Simpson et al., STREPTOCOCCUS-SALIVARIUS ATCC-25975 POSSESSES AT LEAST 2 GENES-CODINGFOR PRIMER-INDEPENDENT GLUCOSYLTRANSFERASES, Infection and immunity, 63(2), 1995, pp. 609-621
Fractionation of the culture medium showed that Streptococcus salivari
us ATCC 25975 secreted a glucosyl-transferase (Gtf) that was primer in
dependent, On the basis of this observation, a gene library of S. sali
varius chromosomal DNA cloned into lambda L47.1 was screened for a gen
e(s) coding for such an activity. As a result of this screening proces
s, two new gtf genes, gtfL and gtfM, both of which coded for primer-in
dependent Gtf activities, were isolated, GtfL produced an insoluble gl
ucan that was refractory to digestion by the endo-(1 --> 6)-alpha-D-gl
ucanase of Chaetonium gracile, while GtfM produced a soluble glucan th
at was readily degraded by the glucanase. Comparison of the deduced am
ino acid sequences of gtfL and gtfM with 10 other available Gtf sequen
ces allowed the relatedness of the conserved catalytic regions to be a
ssessed, This analysis showed that the 12 enzymes did not form cluster
s based on their primer dependencies dr on their product solubilities,
Further analysis of the YG repeats in the C-terminal glucan-binding d
omains of GtfJ, GtfK, GtfL, and GtfM from S. salivarius showed that th
ere was strong homology between a block of contiguous triplet YG repea
ts present in the four alleles. These blocks of YG repeats were coded
for by a region of each gene that appeared to have arisen as a result
of a recent duplication event(s).