Lodwick D, Owen D, Strike P
Department of Genetics and Microbiology, University of Liverpool, UK.
Nucleic Acids Res. 1990 Sep 11;18(17):5045-50. doi: 10.1093/nar/18.17.5045.
The sequence of the imp operon of the plasmid TP110 (which belongs to the Incl1 incompatibility group) has been determined, and is shown to contain three open reading frames. This operon, involved in UV protection and mutation, is functionally analogous to the umuDC operon of E. coli and the mucAB operon of the plasmid pKM101, which belongs to the quite unrelated IncN incompatibility group. The umu and muc operons however contain only two open reading frames, coding for proteins of approximately 16kD and 46kD. The high degree of homology between the two 16kD proteins (UmuD and MucA) and between the two 46kD proteins (UmuC and MucB) clearly shows their relatedness. This is shown also to extend to the imp gene products, with ImpA sharing homology with UmuD and MucA, and ImpB sharing homology with UmuC and MucB. However, the two imp genes are preceded in the operon by a third gene, impC, which encodes a small protein of 9.5kD and which has no equivalent in the umu and muc operons.
质粒TP110（属于Inc1不相容群）的imp操纵子序列已被确定，且显示含有三个开放阅读框。这个参与紫外线防护和突变的操纵子，在功能上类似于大肠杆菌的umuDC操纵子以及质粒pKM101的mucAB操纵子，后者属于完全不相关的IncN不相容群。然而，umu和muc操纵子仅含有两个开放阅读框，编码约16kD和46kD的蛋白质。两种16kD蛋白质（UmuD和MucA）之间以及两种46kD蛋白质（UmuC和MucB）之间的高度同源性清楚地表明了它们的相关性。这也延伸到了imp基因产物，ImpA与UmuD和MucA具有同源性，ImpB与UmuC和MucB具有同源性。然而，在操纵子中，两个imp基因之前还有第三个基因impC，它编码一种9.5kD的小蛋白质，在umu和muc操纵子中没有与之对应的基因。
