Petroni E A, Ielpi L
Instituto de Investigaciones Bioquímicas Fundación Campomar, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
J Bacteriol. 1996 Aug;178(16):4814-21. doi: 10.1128/jb.178.16.4814-4821.1996.
A genetic locus from Acetobacter xylinum involved in acetan polysaccharide synthesis has been characterized. The chromosomal region was identified by screening a genomic library of A. xylinum in a Xanthomonas campestris mutant defective in xanthan polysaccharide synthesis. The A. xylinum cosmid clone can functionally complement a xanthan-negative mutant. The polymer produced by the recombinant strain was found to be indistinguishable from xanthan. Insertion mutagenesis and subcloning of the cosmid clone combined with complementation studies allowed the identification of a 2.3-kb fragment of A. xylinum chromosomal DNA. The nucleotide sequence of this fragment was analyzed and found to contain an open reading frame (aceA) of 1,182 bp encoding a protein of 43.2 kDa. Results from biochemical and genetic analyses strongly suggest that the aceA gene encodes the GDP-mannose:cellobiosyl-diphosphopolyprenol alpha-mannosyltransferase enzyme, which is responsible for the transfer of an alpha-mannosyl residue from GDP-Man to cellobiosyl-diphosphopolyprenol. A search for similarities with other known mannosyltransferases revealed that all bacterial alpha-mannosyltransferases have a short COOH-terminal amino acid sequence in common.
已对木醋杆菌中参与乙酰化多糖合成的一个基因位点进行了表征。通过在黄原胶多糖合成缺陷的野油菜黄单胞菌突变体中筛选木醋杆菌的基因组文库，确定了该染色体区域。木醋杆菌黏粒克隆能够在功能上互补一个黄原胶阴性突变体。发现重组菌株产生的聚合物与黄原胶无法区分。通过对黏粒克隆进行插入诱变、亚克隆并结合互补研究，鉴定出了一段2.3 kb的木醋杆菌染色体DNA片段。对该片段的核苷酸序列进行分析，发现其包含一个1182 bp的开放阅读框（aceA），编码一个43.2 kDa的蛋白质。生化和遗传分析结果强烈表明，aceA基因编码GDP-甘露糖：纤维二糖基二磷酸聚萜醇α-甘露糖基转移酶，该酶负责将一个α-甘露糖基残基从GDP-Man转移至纤维二糖基二磷酸聚萜醇。与其他已知甘露糖基转移酶的相似性搜索显示，所有细菌α-甘露糖基转移酶都有一个共同的短COOH末端氨基酸序列。
