Thompson S A, Wang L L, Sparling P F
Curriculum in Genetics, University of North Carolina, Chapel Hill 27599.
Mol Microbiol. 1993 Jul;9(1):85-96. doi: 10.1111/j.1365-2958.1993.tb01671.x.
Neisseria meningitidis FAM20 has recently been shown to produce two Fe-regulated proteins (FrpA and FrpC) related to the RTX family of cytotoxins. Here we report the cloning and DNA sequence of the locus containing the gene encoding the larger meningococcal RTX protein FrpC. FrpC was highly similar to FrpA throughout much of the predicted protein, with two main differences. Whereas the FrpA protein had 13 copies of the nine-amino-acid repeat units typical of RTX proteins, FrpC had 43 copies. The additional copies in FrpC apparently arose from a threefold tandem amplification of a 600bp DNA fragment encoding the repeats. In addition, the frpC gene lacked good promoter consensus sequences. An open reading frame (ORF1) of unknown function was found immediately upstream of frpC, suggesting the possibility that frpC was cotranscribed with ORF1. A probable promoter was found 300bp upstream of ORF1, and it contained a Fur protein-binding sequence found in the promoters of Fe-regulated Escherichia coli genes. DNA upstream of the ORF1/frpC promoter was homologous to IS1016-like elements surrounding capsulation loci of strains of Haemophilus influenzae. A FrpC-like protein (reactive in immunoblots with monoclonal antibody 9D4; multiple reactive bands of about 200 to 120 kDa) was found in five out of eight meningococcal strains but only in one out of 14 other Neisseria, suggesting that FrpC may participate in the pathogenesis of meningococcal disease.
最近研究表明，脑膜炎奈瑟菌FAM20可产生两种与RTX细胞毒素家族相关的铁调节蛋白（FrpA和FrpC）。本文报道了包含编码较大的脑膜炎球菌RTX蛋白FrpC的基因位点的克隆及DNA序列。在大部分预测蛋白中，FrpC与FrpA高度相似，但存在两个主要差异。FrpA蛋白具有13个RTX蛋白典型的九氨基酸重复单元，而FrpC有43个。FrpC中额外的重复单元显然源于编码这些重复序列的600bp DNA片段的三倍串联扩增。此外，frpC基因缺乏良好的启动子共有序列。在frpC上游紧邻发现一个功能未知的开放阅读框（ORF1），提示frpC可能与ORF1共转录。在ORF1上游300bp处发现一个可能的启动子，其中含有在铁调节的大肠杆菌基因启动子中发现的Fur蛋白结合序列。ORF1/frpC启动子上游的DNA与流感嗜血杆菌菌株荚膜位点周围的IS1016样元件同源。在8株脑膜炎球菌中的5株中发现了一种FrpC样蛋白（在免疫印迹中与单克隆抗体9D4反应；有多个约200至120kDa的反应条带），但在其他14株奈瑟菌中仅在1株中发现，这表明FrpC可能参与脑膜炎球菌病的发病机制。
