Genetical and structural analysis of a group of λilv and λrho transducing phages

Abstract

Eight λilvC transducing phages generated from E. coli K12 secondary site lysogens have been analysed genetically and physically. Two of them carry, in addition, the rho gene and its promotor region, but not the cya gene. The ilvO603 mutation has been located between ilvG and ilvE. Electrophoretic analysis of the proteins synthesized by these phages in a system of UV irradiated cells allowed us to assign molecular weights of 55000 and 66000 daltons to the ilvC and the ilvD gene products, respectively, and to show that an ilvG-encoded polypeptide of 60000 daltons is made from an ilvO^- but not from an ilvO⁺ phage. The expression of the ilvG gene is discussed in the light of the recent finding of a promoter-attenuator region lying upstream to ilvG. Finally, we have found that one of the λilv phages does not have the classical structure of a transducing phage.