Molecular analysis of the UV protection and mutation genes carried by the I incompatibility group plasmid TP110.

The imp genes, responsible for the UV protection and mutation effects of the I incompatibility group plasmid TP110, have been cloned into vector plasmids, and their products have been analyzed. The genetic information required for expression of these properties was carried in a continuous DNA sequence of approximately 1.7 kilobases, encoding the production of two proteins with molecular weights of 11,000 and 51,000. The genetic arrangement of this system therefore appears similar but not identical to the functionally related umuDC and mucAB operons. A third protein with a molecular weight of 40,000 was produced from sequences downstream from imp and could be overproduced by high-level transcription through the imp genes. This protein was not required for the protection and mutation properties.