Glucose-permease of the bacterial phosphotransferase system. Gene cloning, overproduction, and amino acid sequence of enzyme IIGlc

Abstract

The glucose-permease (IIGlc) of the bacterial phosphotransferase system mediates sugar transport across the cytoplasmic membrane concomitant with sugar phosphorylation. It also functions as a receptor for bacterial chemotaxis. The structural gene of the permease, ptsG, has been cloned on a multicopy plasmid, and transformants constitutively overproducing the protein 10-15 times over wild-type level have been isolated. Overproduction is slightly inhibited if transformants are grown in a glucose-containing medium. The complete amino acid sequence of the glucose-permease is deduced from the nucleotide sequence. It consists of 477 residues and is moderately hydrophobic. A comparison of the glucose-permease with the mannitol-permease (Lee, C. A., and Saier, M. H., Jr. (1983) J. Biol. Chem. 258, 10761-10767) does not reveal any obvious homology at the level of amino acid sequence.