Loss of rac locus DNA in merozygotes of Escherichia coli K12.

Summary Two genes governing ribosomal protein methylation have been located on the map of Escherichia coli by conjugation and transduction crosses between wild-type and prm (protein methylation) mutants. The Prm phenotype of recombinants was determined by an in vitro assay of methylgroups incorporation into protein.Gene prmA, governing methylation of protein L11 is situated at minute 71 on the map and is cotransduced with aroE (30%) and with rpsL (5%). Gene prmB, governing methylation of protein L3 is at minute 50, very close to aroC (98.5% co-transduction). A cold-sensitive phenotype was found associated with mutation prmB and was used to score a large number of recombinants in a three factor cross. The results of this cross suggest the order aroC-prmB-purF.The striking symmetrical clustering of aro, prm and rim (ribosome maturation) genes is discussed.