May T, Kocherginskaya S A, Mackie R I, Vercoe P E, White B A
Department of Animal Sciences, University of Illinois at Urbana-Champaign 61801, USA.
FEMS Microbiol Lett. 1996 Nov 1;144(2-3):221-7. doi: 10.1111/j.1574-6968.1996.tb08534.x.
The complete nucleotide sequence of a cryptic plasmid designated pBAW301, from the Gram-positive ruminal bacterium Ruminococcus flavefaciens R13e2, has been determined. This plasmid is 1768 bp in size and has an overall G+C content of 43.5%. Computer analysis of the sequence data revealed an open reading frame, ORF1 (256 amino acids), which is similar to the Rep protein of the Bacillus borstelensis plasmid pHT926. ORF1 is preceded by Shine-Dalgarno and Escherichia coli-10 and -35 like sequences. Nine smaller open reading frames showed no significant homologies to known protein sequences. Analysis of replication intermediates and the nucleotide sequence indicate that the plasmid does not replicate by a rolling-circle mode of replication similar to other plasmids from Gram-positive bacteria. Moreover, sequences typical of theta replication origins were not found in the nucleotide sequence of pBAW301. These data suggest that this plasmid either replicates by an as yet undescribed mechanism, or represents a new class of theta replicating plasmids.
已确定来自革兰氏阳性瘤胃细菌黄化瘤胃球菌R13e2的一个隐蔽质粒pBAW301的完整核苷酸序列。该质粒大小为1768 bp，总体G+C含量为43.5%。对序列数据的计算机分析揭示了一个开放阅读框ORF1（256个氨基酸），它与博斯特芽孢杆菌质粒pHT926的Rep蛋白相似。ORF1之前有Shine-Dalgarno序列以及类似大肠杆菌-10和-35的序列。九个较小的开放阅读框与已知蛋白质序列无明显同源性。对复制中间体和核苷酸序列的分析表明，该质粒不像革兰氏阳性细菌的其他质粒那样通过滚环复制模式进行复制。此外，在pBAW301的核苷酸序列中未发现典型的θ复制起点序列。这些数据表明该质粒要么通过一种尚未描述的机制进行复制，要么代表一类新的θ复制质粒。
