Molecular analysis of representative Streptococcus gordonii Spp phase variants reveals no differences in the glucosyltransferase structural gene, gtfG.
Molecular analysis of representative Streptococcus gordonii Spp phase variants reveals no differences in the glucosyltransferase structural gene, gtfG.
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对代表性戈登链球菌 Spp 相变体的分子分析表明，葡萄糖基转移酶结构基因 gtfG 没有差异。
DOI：
10.1111/j.1399-302x.1997.tb00622.x
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发表时间：
1997
影响因子：
--
通讯作者：
Clewell,DB
中科院分区：
文献类型：
--
作者：
Vickerman,MM;Jones,GW;Clewell,DB
链球菌糖基转移酶聚合蔗糖形成葡聚糖，使蔗糖琼脂平板上的菌落具有硬的蔗糖促进表型(SPP+)。糖基转移酶结构基因gtfG受上游决定簇rgG的正调控。菌株链的葡萄糖转移酶活性在高水平(SPP+)和低水平(SPP−)之间经历了自发的可逆相变。为了深入了解葡萄糖基转移酶阶段变异的基础，对代表性菌株进行了检测。Western blotts结果表明，Spp、−和Spp+菌株的葡萄糖转移酶活性与胞外葡萄糖转移酶蛋白产量有关。SPP+株CH97的rggG和gtfG核苷酸序列与SPP+亲本完全相同，说明这些区域的DNA差异不是葡萄糖基转移酶阶段变异的基础。实际上，~(13)C-核磁共振波谱表明，菌株CH97葡萄糖转移酶合成的葡聚糖与亲本菌株SPP+的葡萄糖转移酶合成的葡聚糖相似，表明这是一个数量上的变化，而不是质量上的变化。然而，一株SPP−菌株CH1c1在RgG上发生了点突变；用CH1c1等位基因替换同源基因会导致葡萄糖转移酶蛋白水平和活性下降。结果表明，葡萄糖转移酶的时相变化可以通过多种方式发生，提示葡萄糖转移酶的调控可能涉及影响转录和/或组织转录因子表达的远端调控基因(S)。
Streptococcus gordoniiglucosyltransferase polymerizes sucrose to form glucans, which confer a hard, sucrose‐promoted phenotype (Spp+) to colonies on sucrose agar plates. The glucosyltransferase structuralgene, gtfG, is positively regulated by the upstream determinant, rgg. Strain Chain's undergoes a spontaneous, reversible phase variation between high (Spp+) and low (Spp−) levels of glucosyltransferase activity. Representative strains were examined to gain insights into the basis of glucosyltransferase phase variation. Western blots indicated that the level of glucosyltransferase activity was related to the amount of extracellular glucosyltransferase protein produced by Spp−and Spp+strains. The nucleotide sequence ofrggandgtfGof the Spp+strain CH97 was found to be identical to that of the Spp+parent, indicating that DNA differences in these regions are not the basis for glucosyltransferase phase variation. Indeed,13C‐NMR spectroscopy suggested that glucans synthesized by strain CH97 glucosyltransferase were similar to those synthesized by glucosyltransferase of the Spp+parental strain, indicating a quantitative rather than qualitative change. However, one Spp−strain, CH1C1, had a point mutation inrgg; replacement of the parentrggwith the CH1C1 allele resulted in decreased levels of glucosyltransferase protein and activity. The results indicate that glucosyltransferase phase variation can occur in more than one way, and suggest that glucosyltransferase regulation may involve distally located regulatory gene(s) that affectrggand/orgtfGexpression.