Pel, the protein that permits λ DNA penetration of Escherichia coli, is encoded by a gene in ptsM and is required for mannose utilization by the phosphotransferase system

Mannose uptake and phosphorylation in Escherichia coli is catalyzed by the phosphoenolpyruvate:glycose phosphotransferase system (PTS). The mannose-specific complex of the PTS, designated II(Man), comprises lipid and two membrane proteins, II-A(Man) and II-B(Man). The proteins are encoded by ptsM, located at ~40 minutes on the E. coli chromosome. A different genetic marker, pel, maps with ptsM, and is required for λ DNA penetration of the cytoplasmic membrane. Earlier studies suggested that both pel function and II-B(Man) are encoded by the same gene, while a different gene (also in ptsM) encodes II-A(Man). In the present studies, a ptsM clone, pCS13, was isolated from an E. coli HindIII gene bank in pBR322 and restored both mannose fermentation and pel⁺ function to ptsM mutants defective in II-B(Man). Subclones of pCS13 show that (i) two distinct genes, manY and manZ, encode the pel⁺ function and the II-B(Man) protein, respectively; (ii) each gene may have its own promoter; (iii) whereas the protein encoded by manY (Pel) alone seems sufficient for λ sensitivity, all three gene products are required for mannose fermentation, transport of the mannose analogue 2-deoxyglucose, and phosphorylation of the latter by cytoplasmic membranes. Thus, Pel is required for function of the II(Man) complex. The efficiency of the complex may depend on the ratio of Pel to II(Man).