Weinrauch Y, Guillen N, Dubnau D A
Department of Microbiology, Public Health Research Institute, New York, New York 10016.
J Bacteriol. 1989 Oct;171(10):5362-75. doi: 10.1128/jb.171.10.5362-5375.1989.
The complete nucleotide sequences of the comA and comB loci of Bacillus subtilis were determined. The products of these genes are required for the development of competence in B. subtilis and for the expression of late-expressing competence genes. The major 5' termini of both the comA and comB transcripts were determined. The inferred promoters of both comA and comB contained sequences that were similar to those found at the -10 and -35 regions of promoters that are used by sigma A-RNA polymerase, the primary form of this enzyme in vegetative cells. The comB gene was located approximately 3 kilobase pairs upstream of the comA gene and encoded a 409-amino-acid protein with a predicted molecular weight of 46,693. The comA locus contained two open reading frames (ORFs) and comB contained one ORF. The predicted amino acid sequence of the comA ORF1 gene product consisted of 214 amino acids, with an aggregate molecular weight of 24,132. The ORF1 product was required for competence, while ORF2, which was cotranscribed with ORF1 and encoded a predicted protein of 126 amino acids, was not. The predicted protein sequence of the comA ORF1 gene product was found to be similar to that of several members of the effector class of procaryotic signal transducers. The C-terminal portion of the predicted comA sequence contained a possible helix-turn-helix motif, which is characteristic of DNA-binding proteins. comA ORF1 was cloned on a multicopy plasmid and was shown to complement the competence-deficient phenotype caused by the comA124 insertion of Tn917lac. Also, the presence of comA ORF1 in multiple copies interfered with sporulation. Anti-peptide antibodies raised to the predicted product of comA ORF1 reacted strongly with a single protein band of about 24,000 daltons in immunoblots. The possible roles of multiple signal transduction systems in triggering the development of competence are discussed.
测定了枯草芽孢杆菌comA和comB基因座的完整核苷酸序列。这些基因的产物是枯草芽孢杆菌感受态发育以及晚期表达的感受态基因表达所必需的。确定了comA和comB转录本的主要5'末端。comA和comB的推测启动子包含的序列，与营养细胞中该酶的主要形式——σA-RNA聚合酶所使用的启动子的-10和-35区域的序列相似。comB基因位于comA基因上游约3千碱基对处，编码一个409个氨基酸的蛋白质，预测分子量为46,693。comA基因座包含两个开放阅读框（ORF），comB包含一个ORF。comA ORF1基因产物的预测氨基酸序列由214个氨基酸组成，总分子量为24,132。ORF1产物是感受态所必需的，而与ORF1共转录并编码一个预测的126个氨基酸蛋白质的ORF2则不是。发现comA ORF1基因产物的预测蛋白质序列与原核信号转导器效应器类的几个成员相似。预测的comA序列的C末端部分包含一个可能的螺旋-转角-螺旋基序，这是DNA结合蛋白的特征。comA ORF1被克隆到一个多拷贝质粒上，并显示出能够互补由Tn917lac的comA124插入所导致的感受态缺陷表型。此外，多拷贝的comA ORF1的存在会干扰芽孢形成。针对comA ORF1预测产物产生的抗肽抗体在免疫印迹中与一条约24,000道尔顿的单一蛋白带强烈反应。讨论了多种信号转导系统在触发感受态发育中的可能作用。
