NUCLEOTIDE-SEQUENCE AND GENETIC-ANALYSIS OF THE NEUD AND NEUB GENES IN REGION-2 OF THE POLYSIALIC ACID GENE-CLUSTER OF ESCHERICHIA-COLI-K1
NUCLEOTIDE-SEQUENCE AND GENETIC-ANALYSIS OF THE NEUD AND NEUB GENES IN REGION-2 OF THE POLYSIALIC ACID GENE-CLUSTER OF ESCHERICHIA-COLI-K1
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DOI：
10.1128/jb.177.2.312-319.1995
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发表时间：
1995-01-01
影响因子：
3.2
通讯作者：
SILVER, RP
中科院分区：
文献类型：
--
作者：
ANNUNZIATO, PW;WRIGHT, LF;SILVER, RP
K1荚膜多糖是一种唾液酸聚合物，是肠外致病性大肠杆菌的重要毒力决定因子。对大肠杆菌多聚唾液酸囊膜的合成和表达基因进行了克隆和分析。Call K1位于17-kb kps基因簇上，该基因簇在功能上分为三个区域。中心区域2编码唾液酸合成、活化和聚合所必需的蛋白质，而侧翼区域1和3参与聚合物转运至细胞表面。在这项研究中，我们确定了两个基因的近端区域2，neuD和neuB，其编码的蛋白质与预测的大小分别为22.7和38.7 kDa。一些观察结果表明，neuB基因编码唾液酸合成酶。EV 24是一种neuB染色体突变体，当提供外源唾液酸时表达包膜，可以通过克隆的neuB基因反式互补。此外，NeuB与脑膜炎奈瑟菌B群的cps B基因产物具有显著的序列相似性，该基因被假定编码唾液酸合酶。我们还提出的数据表明，neuD在K1聚合物生产中起着至关重要的作用。携带pSR 426的细胞产生细胞内聚合物，pSR 426包含所有区域2但缺乏区域1和3基因。相反，在携带缺乏功能性neuD基因的pSR 426衍生物的细胞中没有聚合物积累。然而，与neuB突变的菌株不同，neuD突变体不被外源性唾液酸补充，表明NeuD不参与唾液酸合成。此外，在neuD中携带突变的细胞积累唾液酸和CMP-唾液酸。我们还发现neuD突变体和野生型生物体的内源性和外源性唾液酸转移酶活性之间没有显着差异。NeuD与一个细菌乙酰转移酶家族具有显著的相似性，这导致了NeuD是一种乙酰转移酶，可能通过修饰其他2区蛋白发挥其影响的理论。
The K1 capsular polysaccharide, a polymer of sialic acid, is an important virulence determinant of extraintestinal pathogenic Escherichia coli. The genes responsible for the synthesis and expression of the polysialic acid capsule of E. call K1 are located on the 17-kb kps gene cluster, which is functionally divided into three regions. Central region 2 encodes proteins necessary for the synthesis, activation, and polymerization of sialic acid, while flanking regions 1 and 3 are involved in polymer transport to the cell surface. In this study, we identified two genes at the proximal end of region 2, neuD and neuB, which encode proteins with predicted sizes of 22.7 and 38.7 kDa, respectively. Several observations suggest that the neuB gene encodes sialic acid synthase. EV24, a neuB chromosomal mutant that expresses a capsule when provided exogenous sialic acid, could be complemented in trans by the cloned neuB gene. In addition, NeuB has significant sequence similarity to the product of the cpsB gene of Neisseria meningitidis group B, which is postulated to encode sialic acid synthase. We also present data indicating that neuD has an essential role in K1 polymer production. Cells harboring pSR426, which contains all of region 2 but lacks region 1 and 3 genes, produce an intracellular polymer. In contrast, no polymer accumulated in cells carrying a derivative of pSR426 lacking a functional neuD gene. Unlike strains with mutations in neuB, however, neuD mutants are not complemented by exogenous sialic acid, suggesting that NeuD is not involved in sialic acid synthesis. Additionally, cells harboring a mutation in neuD accumulated sialic acid and CMP-sialic acid. We also found no significant differences between the endogenous and exogenous sialyltransferase activities of a neuD mutant and the wild-type organism. NeuD shows significant similarity to a family of bacterial acetyltransferases, leading to the theory that NeuD is an acetyltransferase which may exert its influeuce through modification of other region 2 proteins.