Close Linkage between a Galactose Binding Protein and the β‐Methylgalactoside Permease in Escherichia coli

It has been found that a gene necessary for the production of the galactose binding protein is closely linked, if not identical with the gene(s) determining the β‐methylgalactoside permease. This was determined by crossing a galactose binding protein negative, β‐methylgalactoside permease negative strain of E. coli K‐12 with wild type donor strains. In addition, after mutagenation of a permease positive, binding protein positive strain of E. coli K‐12 with N ‐methyl, N ‐nitroso, N′ ‐nitroguanidine, some of the β‐methylgalactoside permease defective mutants showed concomitant changes in the galactose binding protein. Out of 28 independent permease defective mutants two had lost their ability to produce cross reacting material against antibodies specific for the galactose binding protein; four mutants showed temperature sensitive synthesis of cross reacting material; five mutants had immunochemically somewhat changed binding protein. The immunochemical assay showed no changes in the binding protein of the rest of the 17 mutants. However, the galactose binding activity of the crude extract of these mutants varied to a great extent (10–90%) from the activity‐found in the crude extract of the wild type. These results suggest a close relationship between the galactose binding protein and the β‐methylgalactoside permease.