Nucleotide sequence analysis of the Streptococcus gordonii glucosyltransferase gene, gtfG
Nucleotide sequence analysis of the Streptococcus gordonii glucosyltransferase gene, gtfG
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DOI：
10.3109/10425179709020155
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发表时间：
1997-01-01
期刊：
影响因子：
--
通讯作者：
Clewell, DB
中科院分区：
文献类型：
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作者：
Vickerman, MM;Sulavik, MC;Clewell, DB
古登链球菌具有细胞外葡糖基转移酶（GTF），其聚合蔗糖的葡萄糖部分以形成水溶性和水不溶性葡聚糖。尽管在变形链球菌和唾液链球菌的菌株中已经鉴定出多个gtf基因，但是命名为gtfG的单个基因编码S的GTF。戈登氏查利斯。gtfG在所表征的gtfs中也是独特的，因为它具有所描述的调节决定子rgg。此外，S. gordonii在高和低能级之间经历可逆的相位变化。为了深入了解这种新的GTF系统，测定了gtfG的核苷酸序列，发现其由4，734个碱基对的开放阅读框组成，编码一种推定分子量为约1000的蛋白质。174,000. gtfG与其他已测序的gtf相似，具有保守的信号序列，随后是ca. 600 bp的区域是gtfG特有的，这是一个保守区域，编码一个推定的催化活性位点和一系列涉及葡聚糖结合的羧基末端区域中的六个直接重复序列。虽然gtfG与其他gtf的比较没有显示编码酶的引物独立性或葡聚糖产物的性质的基础，但gtfG序列数据为这些酶的进一步研究提供了重要基础。
Streptococcus goudonii has an extracellular glucosyltransferase (GTF) that polymerizes the glucose moiety of sucrose to form both water-soluble and water-insoluble glucans. Whereas multiple gtf genes have been identified in strains of mutans streptococci and Streptococcus salivarius, a single gene, designated gtfG, encodes the GTF of S. gordonii Challis. gtfG is also unique among the characterized gtfs in that it has a described regulatory determinant, rgg. Furthermore, the GTF activity in S. gordonii undergoes reversible phase variation between high and low levels. hi order to gain insight into this novel GTF system, the nucleotide sequence of gtfG was determined and found to consist of a 4,734 base pair open reading frame encoding a protein with a deduced molecular weight of ca. 174,000. gtfG was similar to other sequenced gtfs with a conserved signal sequence followed by a ca. 600-bp region distinctive for gtfG, a conserved region encoding a putative catalytic active site and a series of six direct repeats in the carboxyl terminal region implicated in glucan binding. Although comparison of gtfG to other gtfs did not show a basis for the primer-independence of the encoded enzyme or the nature of the glucan products, the gtfG sequence data provide an important basis for further studies of these enzymes.