Hahn J, Inamine G, Kozlov Y, Dubnau D
Public Health Research Institute, New York, New York 10016.
Mol Microbiol. 1993 Oct;10(1):99-111. doi: 10.1111/j.1365-2958.1993.tb00907.x.
The binding and transport of DNA by competent Bacillus subtilis requires the assembly of a specialized apparatus. We present here the characterization of comE, an operon under competence control that is required for both DNA binding to the competent cell surface, and for uptake. comE contains three open reading frames (ORF1-3) read in the forward direction, preceded by a long untranslated leader sequence and an apparent E sigma A promoter. A minor promoter also is responsible for transcription of ORF2 and -3. A transcript containing a single ORF is produced in the reverse direction. The reverse ORF overlaps ORF1 and the untranslated comE leader. The comE transcript is present at a very low level during growth and at an elevated level in stationary-phase cells. Conversely, the reverse transcript is present during exponential growth and disappears during stationary phase. The reverse ORF resembles prokaryotic and eukaryotic pyrroline-5'-carboxylate reductases, while ORF2 is similar to several dCMP deaminases. ORF1 and ORF3 are predicted to be integral membrane proteins. The latter is specifically required for DNA uptake but not for binding.
感受态枯草芽孢杆菌对DNA的结合与转运需要一种特殊装置的组装。我们在此展示了comE的特性，它是一个受感受态控制的操纵子，对于DNA与感受态细胞表面的结合以及摄取均是必需的。comE包含三个正向阅读的开放阅读框（ORF1 - 3），其前面有一个长的非翻译前导序列和一个明显的E σA启动子。一个次要启动子也负责ORF2和ORF3的转录。一个包含单个ORF的转录本以反向产生。反向ORF与ORF1和非翻译的comE前导序列重叠。comE转录本在生长期间水平极低，而在稳定期细胞中水平升高。相反，反向转录本在指数生长期存在，在稳定期消失。反向ORF类似于原核和真核的吡咯啉 - 5'-羧酸还原酶，而ORF2类似于几种dCMP脱氨酶。ORF1和ORF3预计为整合膜蛋白。后者对于DNA摄取是特异性必需的，但对于结合则不是。
