Billington S J, Huggins A S, Johanesen P A, Crellin P K, Cheung J K, Katz M E, Wright C L, Haring V, Rood J I
Department of Microbiology, Monash University, Clayton, Victoria 3168, Australia.
Infect Immun. 1999 Mar;67(3):1277-86. doi: 10.1128/IAI.67.3.1277-1286.1999.
The vrl locus is preferentially associated with virulent isolates of the ovine footrot pathogen, Dichelobacter nodosus. The complete nucleotide sequence of this 27.1-kb region has now been determined. The data reveal that the locus has a G+C content much higher than the rest of the D. nodosus chromosome and contains 22 open reading frames (ORFs) encoding products including a putative adenine-specific methylase, two potential DEAH ATP-dependent helicases, and two products with sequence similarity to a bacteriophage resistance system. These ORFs are all in the same orientation, and most are either overlapping or separated by only a few nucleotides, suggesting that they comprise an operon and are translationally coupled. Expression vector studies have led to the identification of proteins that correspond to many of these ORFs. These data, in combination with evidence of insertion of vrl into the 3' end of an ssrA gene, are consistent with the hypothesis that the vrl locus was derived from the insertion of a bacteriophage or plasmid into the D. nodosus genome.
vrl基因座优先与羊足腐病病原体结节拟杆菌的强毒株相关联。现已确定该27.1 kb区域的完整核苷酸序列。数据显示，该基因座的G+C含量远高于结节拟杆菌染色体的其余部分，包含22个开放阅读框（ORF），其编码产物包括一种假定的腺嘌呤特异性甲基化酶、两种潜在的依赖DEAH ATP的解旋酶，以及两种与噬菌体抗性系统具有序列相似性的产物。这些开放阅读框均为同一方向，且大多数要么重叠，要么仅相隔几个核苷酸，这表明它们构成一个操纵子并在翻译上偶联。表达载体研究已鉴定出与其中许多开放阅读框相对应的蛋白质。这些数据，再加上vrl插入到ssrA基因3'端的证据，与vrl基因座源自噬菌体或质粒插入结节拟杆菌基因组的假说一致。
