Marsh J W, Taylor R K
Department of Microbiology, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
J Bacteriol. 1999 Feb;181(4):1110-7. doi: 10.1128/JB.181.4.1110-1117.1999.
The mannose-sensitive hemagglutinin (MSHA) of the Vibrio cholerae O1 El Tor biotype is a member of the family of type 4 pili. Type 4 pili are found on the surface of a variety of gram-negative bacteria and have demonstrated importance as host colonization factors, bacteriophage receptors, and mediators of DNA transfer. The gene locus required for the assembly and secretion of the MSHA pilus has been localized to a 16.7-kb region of the V. cholerae chromosome. Sixteen genes required for hemagglutination, including five that encode prepilin or prepilin-like proteins, have been identified. Examination of MSHA-specific cDNAs has localized two promoters that drive expression of these genes. This evidence indicates that the MSHA gene locus is transcriptionally organized into two operons, one encoding the secretory components and the other encoding the structural subunits, an arrangement unique among previously characterized type 4 pilus loci. The genes flanking the MSHA locus encode proteins that show homology to YhdA and MreB of Escherichia coli. In E. coli, the yhdA and mreB genes are adjacent to each other on the chromosome. The finding that the MSHA locus lies between these two E. coli homologs and that it is flanked by a 7-bp direct repeat suggests that the MSHA locus may have been acquired as a mobile genetic element.
霍乱弧菌O1 El Tor生物型的甘露糖敏感血凝素（MSHA）是4型菌毛家族的成员。4型菌毛存在于多种革兰氏阴性菌的表面，已被证明作为宿主定植因子、噬菌体受体和DNA转移介质具有重要意义。MSHA菌毛组装和分泌所需的基因座已定位到霍乱弧菌染色体的一个16.7 kb区域。已鉴定出16个血凝所需基因，包括5个编码前菌毛蛋白或前菌毛样蛋白的基因。对MSHA特异性cDNA的研究已定位到驱动这些基因表达的两个启动子。这一证据表明，MSHA基因座在转录上被组织成两个操纵子，一个编码分泌成分，另一个编码结构亚基，这种排列在先前表征的4型菌毛基因座中是独特的。MSHA基因座两侧的基因编码与大肠杆菌的YhdA和MreB具有同源性的蛋白质。在大肠杆菌中，yhdA和mreB基因在染色体上彼此相邻。MSHA基因座位于这两个大肠杆菌同源物之间且两侧有一个7 bp直接重复序列的发现表明，MSHA基因座可能是作为一个可移动遗传元件获得的。
