Goodman S D, Scocca J J
Department of Biochemistry, Johns Hopkins University School of Hygiene and Public Health, Baltimore, MD 21205.
Proc Natl Acad Sci U S A. 1988 Sep;85(18):6982-6. doi: 10.1073/pnas.85.18.6982.
DNA segments from Neisseria gonorrhoeae, cloned and propagated in Escherichia coli, were tested for the ability to competitively inhibit gonococcal transformation. The nucleotide sequences of active segments were determined and compared; these sequences contained the sequence 5' GCCGTCTGAA 3' in common. Subcloning studies confirmed the identity of this sequence as the gonococcal DNA recognition site. The three instances of the recognition sequence isolated from N. gonorrhoeae chromosomal DNA contain the sequence in the immediate neighborhood of its inverted repeat. Because a single copy of the sequence functions as a recognition site, the inverted duplication is not required for specific binding. The dyad symmetric arrangements of the chromosomal recognition sequences may form stable stem-loop structures that can function as terminators or attenuators of transcription. These inverted repeats are located at the boundaries of long open reading frames. The recognition sequence also constitutes part of two other probable terminators of gonococcal genes. We conclude that the signal for recognition of transforming DNA by gonococci is a frequent component of transcriptional terminator sequences. This regulatory function might account for the origin and maintenance of recognition sequences in the chromosomes of Gram-negative transformable bacteria.
对在大肠杆菌中克隆和繁殖的淋病奈瑟菌的DNA片段进行了测试,以检测其竞争性抑制淋球菌转化的能力。测定并比较了活性片段的核苷酸序列;这些序列共同包含序列5' GCCGTCTGAA 3'。亚克隆研究证实了该序列作为淋球菌DNA识别位点的身份。从淋病奈瑟菌染色体DNA中分离出的三个识别序列实例在其反向重复序列的紧邻区域包含该序列。由于该序列的单个拷贝起识别位点的作用,因此特异性结合不需要反向重复。染色体识别序列的二元对称排列可能形成稳定的茎环结构,其可作为转录的终止子或衰减子。这些反向重复位于长开放阅读框的边界。识别序列还构成了淋球菌基因的另外两个可能的终止子的一部分。我们得出结论,淋球菌识别转化DNA的信号是转录终止子序列的常见组成部分。这种调节功能可能解释了革兰氏阴性可转化细菌染色体中识别序列的起源和维持。