Physical and genetic structure of the glpD-malT interval of the Escherichia coli K-12 chromosome. Identification of two new structural genes of the glp-regulon.

A transducing lambda phage carrying glpD''lacZ, glpR, and malT was isolated from a strain harboring a glpD''lacZ fusion. Comparison of restriction endonuclease cleavage patterns of DNA isolated from this phage with that of the previously cloned malT region (Raibaud and Schwartz 1980) facilitated the construction of recombinant plasmids carrying different portions of the glpD-malT region. Results of minicell analysis and complementation studies showed that this region of the chromosome encodes at least five polypeptides. These included the previously identified glpD, glpR, and malT gene products. In addition, two new structural genes of the glp regulon (glpE and glpG) located between the glpD and glpR genes were identified. Hybrid plasmids carrying glpD''lacZ and glpR''lacZ fusions were constructed. Restriction endonuclease cleavage analysis of these two plasmids demonstrated that glpD and glpR are divergently transcribed.