Kiss E, Reuhs B L, Kim J S, Kereszt A, Petrovics G, Putnoky P, Dusha I, Carlson R W, Kondorosi A
Institute of Genetics, Biological Research Center, Hungarian Academy of Sciences, Szeged.
J Bacteriol. 1997 Apr;179(7):2132-40. doi: 10.1128/jb.179.7.2132-2140.1997.
The first complementation unit of the fix-23 region of Rhizobium meliloti, which comprises six genes (rkpAB-CDEF) exhibiting similarity to fatty acid synthase genes, is required for the production of a novel type of capsular polysaccharide that is involved in root nodule development and structurally analogous to group II K antigens found in Escherichia coli (G. Petrovics, P. Putnoky, R. Reuhs, J. Kim, T. A. Thorp, K. D. Noel, R. W. Carlson, and A. Kondorosi, Mol. Microbiol. 8:1083-1094, 1993; B. L. Reuhs, R. W. Carlson, and J. S. Kim, J. Bacteriol. 175:3570-3580, 1993). Here we present the nucleotide sequence for the other three complementation units of the fix-23 locus, revealing the presence of four additional open reading frames assigned to genes rkpGHI and -J. The putative RkpG protein shares similarity with acyltransferases, RkpH is homologous to short-chain alcohol dehydrogenases, and RkpJ shows significant sequence identity with bacterial polysaccharide transport proteins, such as KpsS of E. coli. No significant homology was found for RkpI. Biochemical and immunological analysis of Tn5 derivatives for each gene demonstrated partial or complete loss of capsular polysaccharides from the cell surface; on this basis, we suggest that all genes in the fix-23 region are required for K-antigen synthesis or transport.
苜蓿根瘤菌fix - 23区域的第一个互补单位包含六个与脂肪酸合酶基因相似的基因（rkpAB - CDEF），该单位对于一种新型荚膜多糖的产生是必需的，这种荚膜多糖参与根瘤发育，并且在结构上类似于大肠杆菌中发现的II型K抗原（G. Petrovics，P. Putnoky，R. Reuhs，J. Kim，T. A. Thorp，K. D. Noel，R. W. Carlson和A. Kondorosi，《分子微生物学》8：1083 - 1094，1993；B. L. Reuhs，R. W. Carlson和J. S. Kim，《细菌学杂志》175：3570 - 3580，1993）。在此，我们展示了fix - 23位点其他三个互补单位的核苷酸序列，揭示了另外四个开放阅读框，它们被指定为基因rkpGHI和 - J。推测的RkpG蛋白与酰基转移酶具有相似性，RkpH与短链醇脱氢酶同源，并且RkpJ与细菌多糖转运蛋白（如大肠杆菌的KpsS）具有显著的序列同一性。未发现RkpI有明显的同源性。对每个基因的Tn5衍生物进行的生化和免疫分析表明，细胞表面的荚膜多糖部分或完全缺失；基于此，我们认为fix - 23区域中的所有基因对于K抗原的合成或转运都是必需的。
