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首页> 外文期刊>Infection and immunity >Isolation of a glucan-binding domain of glucosyltransferase (1,6-alpha-glucan synthase) from Streptococcus sobrinus.
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Isolation of a glucan-binding domain of glucosyltransferase (1,6-alpha-glucan synthase) from Streptococcus sobrinus.

机译：从链球菌中分离出葡糖基转移酶（1，6-α-葡聚糖合酶）的葡聚糖结合结构域。

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A glucan-binding domain of 1,6-alpha-glucan synthase (dextransucrase) (GTF-S) was isolated from a trypsin digest of the Streptococcus sobrinus enzyme. The large 60.5-kilodalton peptide had an affinity for dextran comparable to that of the native enzyme, but had no glucan synthesis activity. The domain was produced in high yield compared with other large cleavage products, which allowed easy purification by size exclusion high-pressure liquid chromatography and affinity chromatography. Two other proteases (mouse submaxillaris protease and lysyl endopeptidase) with specificities similar to trypsin generated a distribution of GTF-S peptides that was also greatly enriched in the glucan-binding peptide. Proteases with markedly different specificities (chymotrypsin and Staphylococcus aureus V8 protease) produced a family of peptides with some evidence of the glucan-binding domain but in far lower yield. The tertiary structure of the domain was critical to its resistance to proteolysis; heat denaturation of GTF-S before trypsin digestion resulted in cleavage of the enzyme to small limit peptides leaving no evidence of the glucan-binding domain. The amino acid composition of the peptide was very similar to that of the native enzyme. The common occurrence of proteases in oral streptococcus cultures and reports of glucosyltransferase degradation during purification and storage raises the possibility that some accounts of glucan-binding receptors are peptides derived from glucosyltransferase. Kinetic implications of a glucan-binding domain are discussed.
机译：从链霉菌链球菌酶的胰蛋白酶消化物中分离出1，6-α-葡聚糖合酶（葡聚糖转氨酶）（GTF-S）的葡聚糖结合结构域。大的60.5-千屈顿肽对葡聚糖具有与天然酶相当的亲和力，但没有葡聚糖合成活性。与其他大裂解产物相比，该结构域的产率高，可通过尺寸排阻高压液相色谱和亲和色谱法轻松纯化。具有与胰蛋白酶相似的特异性的另外两种蛋白酶（小鼠颌下腺蛋白酶和赖氨酰内肽酶）产生了GTF-S肽分布，该分布也大大丰富了葡聚糖结合肽。具有明显不同特异性的蛋白酶（胰凝乳蛋白酶和金黄色葡萄球菌V8蛋白酶）产生的肽家族具有葡聚糖结合结构域的某些证据，但产率低得多。该域的三级结构对其抗蛋白水解作用至关重要。胰蛋白酶消化之前，GTF-S的热变性导致该酶裂解为小限度的肽，而没有葡聚糖结合域的迹象。肽的氨基酸组成与天然酶非常相似。蛋白酶在口腔链球菌培养物中的普遍发生以及在纯化和储存过程中葡糖基转移酶降解的报道增加了某些说明葡聚糖结合受体是衍生自葡糖基转移酶的肽的可能性。讨论了葡聚糖结合域的动力学含义。

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