Heilmann C, Schweitzer O, Gerke C, Vanittanakom N, Mack D, Götz F
Universität Tübingen, Germany.
Mol Microbiol. 1996 Jun;20(5):1083-91. doi: 10.1111/j.1365-2958.1996.tb02548.x.
The Staphylococcus epidermidis genes icaABC are involved in the synthesis of the polysaccharide intercellular adhesin (PIA), which is located mainly on the cell surface, as shown by immunofluorescence studies with PIA-specific antiserum. PIA was shown to be a linear beta-1,6-linked glucosaminoglycan composed of at least 130 2-deoxy-2-amino-D-glucopyranosyl residues of which 80-85% are N-acetylated, the rest being non-N-acetylated and positively charged. A transposon insertion in the icaABC gene cluster (ica, intercellular adhesion) led to the loss of several traits, such as the ability to form a biofilm on a polystyrene surface, cell aggregation, and PIA production. The mutant could be complemented by transformation with the icaABC-carrying plasmid pCN27. Transfer of pCN27 into the heterologous host Staphylococcus carnosus led to the formation of large cell aggregates, the formation of a biofilm on a glass surface, and PIA expression. The nucleotide sequence of icaABC suggests that the three genes are organized in an operon and that they are co-transcribed from the mapped icaA promoter. IcaA contains four potential transmembrane helices, indicative of a membrane location. The deduced IcaA sequence shows similarity to those of polysaccharide-polymerizing enzymes, the most pronounced being with a Rhizobium meliloti N-acetylglucosaminyltransferase involved in lipo-chitin biosynthesis (22.5% overall identity and 37.4% overall similarity). This similarity suggests that IcaA has N-acetylglucosaminyltransferase activity in the formation of the beta-1, 6-linked N-acetyl-D-glucosaminyl polymer. IcaB is secreted into the medium and contains a typical signal peptide. IcaC is hydrophobic and contains six predicted transmembrane helices distributed over its entire length, typical for an integral membrane protein. Neither IcaB nor IcaC shares similarity with known proteins, and their function is unknown. Inactivation of icaA, icaB, or icaC in pCN27 led to the complete loss of the intercellular adhesion phenotype in S. carnosus, suggesting that all three genes are involved in intercellular adhesion, PIA expression, and translocation.
表皮葡萄球菌icaABC基因参与胞间多糖黏附素（PIA）的合成，PIA主要位于细胞表面，这是通过用PIA特异性抗血清进行免疫荧光研究得出的结果。PIA被证明是一种线性的β-1,6-连接的葡糖胺聚糖，由至少130个2-脱氧-2-氨基-D-吡喃葡糖基残基组成，其中80-85%是N-乙酰化的，其余是非N-乙酰化且带正电荷的。icaABC基因簇（ica，胞间黏附）中的转座子插入导致了几个性状的丧失，如在聚苯乙烯表面形成生物膜的能力、细胞聚集和PIA产生。该突变体可用携带icaABC的质粒pCN27进行互补转化。将pCN27转入异源宿主肉葡萄球菌导致形成大的细胞聚集体、在玻璃表面形成生物膜以及PIA表达。icaABC的核苷酸序列表明这三个基因以操纵子形式组织，并且它们从定位的icaA启动子共转录。IcaA包含四个潜在的跨膜螺旋，表明其位于膜上。推导的IcaA序列与多糖聚合酶的序列相似，与参与脂壳多糖生物合成的苜蓿根瘤菌N-乙酰葡糖胺基转移酶最为相似（总体同一性为22.5%，总体相似性为37.4%）。这种相似性表明IcaA在形成β-1,6-连接的N-乙酰-D-葡糖胺基聚合物中具有N-乙酰葡糖胺基转移酶活性。IcaB分泌到培养基中并含有典型的信号肽。IcaC是疏水的，含有六个预测的跨膜螺旋，分布在其整个长度上，这是整合膜蛋白的典型特征。IcaB和IcaC与已知蛋白质均无相似性，其功能未知。pCN27中icaA、icaB或icaC的失活导致肉葡萄球菌胞间黏附表型完全丧失，表明这三个基因均参与胞间黏附、PIA表达和转运。
