Inouye S, Herzer P J, Inouye M
Department of Biochemistry, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway 08854.
Proc Natl Acad Sci U S A. 1990 Feb;87(3):942-5. doi: 10.1073/pnas.87.3.942.
A reverse transcriptase (RT) was recently found in Myxococcus xanthus, a Gram-negative soil bacterium. This RT has been shown to be associated with a chromosomal region designated a retron responsible for the synthesis of a peculiar extrachromosomal DNA called msDNA (multicopy single-stranded DNA). We demonstrate that M. xanthus contains two independent, unlinked retrons, one for the synthesis of msDNA-Mx162 and the other for msDNA-Mx65. The structural analysis of the retron for msDNA-Mx65 revealed that the coding regions for msdRNA (msr) and msDNA (msd), and an open reading frame (ORF) downstream of msr are arranged in the same manner as found for the Mx162 retron. The ORF encodes a polypeptide of 427 amino acid residues. The amino-terminal domain (residues 1-138) shows no striking similarity to these proteins presently available in the data bases including the msDNA-Mx162 ORF, while the sequence from residues 139-394 can be aligned with various known RT sequences and has 47% identity with the RT domain of the msDNA-Mx162 ORF. On the basis of these findings, possible origins of two highly diverse retrons on the M. xanthus chromosome are discussed.
最近在革兰氏阴性土壤细菌黄色粘球菌中发现了一种逆转录酶（RT）。这种RT已被证明与一个被称为逆转录子的染色体区域相关，该区域负责合成一种特殊的染色体外DNA，称为msDNA（多拷贝单链DNA）。我们证明黄色粘球菌含有两个独立的、不连锁的逆转录子，一个用于合成msDNA-Mx162，另一个用于合成msDNA-Mx65。对msDNA-Mx65逆转录子的结构分析表明，msdRNA（msr）和msDNA（msd）的编码区域，以及msr下游的一个开放阅读框（ORF），其排列方式与Mx162逆转录子相同。该ORF编码一个由427个氨基酸残基组成的多肽。氨基末端结构域（第1-138位残基）与数据库中目前可用的这些蛋白质没有明显的相似性，包括msDNA-Mx162 ORF，而第139-394位残基的序列可以与各种已知的RT序列比对，并且与msDNA-Mx162 ORF的RT结构域有47%的同一性。基于这些发现，讨论了黄色粘球菌染色体上两个高度不同的逆转录子的可能起源。
