Londoño-Vallejo J A, Dubnau D
Public Health Research Institute, New York, New York 10016.
Mol Microbiol. 1993 Jul;9(1):119-31. doi: 10.1111/j.1365-2958.1993.tb01674.x.
We have sequenced and genetically characterized comF, a Bacillus subtilis competence locus, previously identified by Tn917 transposon insertion mutagenesis. Expression of the locus, in which three open reading frames (ORFs) were found, is driven by a single sigma A-like promoter in front of comFORF1 and is dependent on early regulatory competence genes and only expressed in competence medium. The predicted amino acid sequences of two of the ORFs showed similarities to known proteins in the GenBank and SwissProt databases: ComFORF1 is similar to an extensive family of ATP-dependent RNA/DNA helicases with closer similarity to the DEAD protein subfamily and to the PriA protein in Escherichia coli. The latter is a DNA translocase/helicase required for primosome assembly at the replication fork of phage phi X174. ComFORF3 is 22% identical to Com101, a protein required for genetic competence in Haemophilus influenzae, a naturally competent Gram-negative bacterium. In-frame comFORF1 deletions were 1000-fold deficient in transformability compared to the wild-type, whereas disruptions of the other two ORFs were only five- to 10-fold lower. These observations allow us to hypothesize that the ComFORF1 late gene product plays an essential role during the binding and uptake events involved in Bacillus subtilis transformation.
我们已对枯草芽孢杆菌感受态基因座comF进行了测序和遗传特征分析，该基因座先前是通过Tn917转座子插入诱变鉴定出来的。该基因座含有三个开放阅读框（ORF），其表达由comFORF1前的一个单一的σA样启动子驱动，并且依赖于早期调控感受态基因，且仅在感受态培养基中表达。其中两个ORF的预测氨基酸序列与GenBank和SwissProt数据库中的已知蛋白质相似：ComFORF1与一个广泛的ATP依赖性RNA/DNA解旋酶家族相似，与DEAD蛋白亚家族以及大肠杆菌中的PriA蛋白更为相似。后者是噬菌体phi X174复制叉处引发体组装所需的一种DNA转位酶/解旋酶。ComFORF3与流感嗜血杆菌（一种天然感受态革兰氏阴性菌）遗传感受态所需的Com101蛋白有22%的同一性。与野生型相比，框内缺失comFORF1的菌株转化能力缺陷1000倍，而另外两个ORF的破坏仅使转化能力降低5至10倍。这些观察结果使我们能够推测，ComFORF1晚期基因产物在枯草芽孢杆菌转化所涉及的结合和摄取事件中起重要作用。
