Roosendaal E, Boots M, de Graaf F K
Nucleic Acids Res. 1987 Aug 11;15(15):5973-84. doi: 10.1093/nar/15.15.5973.
The nucleotide sequence of the region located transcriptionally upstream of the K99 fimbrial subunit gene (fanC) was determined. Several putative transcription signals and two open reading frames, designated fanA and fanB, became apparent. Frameshift mutations in fanA and fanB reduced K99 fimbriae expression 8-fold and 16-fold, respectively. Complementation of the mutants in trans restored the K99 expression to about 75% of the wild type level, indicating that fanA and fanB code for transacting polypeptides involved in the biogenesis of K99 fimbriae. The fanA and fanB gene products FanA and FanB were not detectable in minicell preparations, indicating that both polypeptides are synthesized in very small amounts. However, in an in vitro DNA directed translation system FanA and FanB could be identified. The deduced amino acid sequences of FanA and FanB showed that both polypeptides contain no signal peptides, indicating a cytoplasmic location. Furthermore, the polypeptides are very hydrophilic, mainly basic, and exhibit remarkable homology to each other and to a regulatory protein (papB) encoded by the pap-operon (1). Some of these features are characteristics of nucleic acid binding proteins, which suggests that FanA and FanB have a regulatory function in the synthesis of FanC and the auxiliary polypeptides FanD-H.
测定了位于K99菌毛亚基基因（fanC）转录上游区域的核苷酸序列。发现了几个推定的转录信号以及两个开放阅读框，分别命名为fanA和fanB。fanA和fanB中的移码突变分别使K99菌毛表达降低了8倍和16倍。通过反式互补突变体可将K99表达恢复到野生型水平的约75%，这表明fanA和fanB编码参与K99菌毛生物合成的反式作用多肽。在小细胞制备物中未检测到fanA和fanB基因产物FanA和FanB，这表明这两种多肽的合成量都非常少。然而，在体外DNA指导的翻译系统中可以鉴定出FanA和FanB。FanA和FanB的推导氨基酸序列表明，这两种多肽都不包含信号肽，表明它们位于细胞质中。此外，这些多肽具有很强的亲水性，主要呈碱性，并且彼此之间以及与由pap操纵子编码的调节蛋白（papB）具有显著的同源性（1）。这些特征中的一些是核酸结合蛋白的特性，这表明FanA和FanB在FanC和辅助多肽FanD - H的合成中具有调节功能。
