Carbohydrate transporters of the bacterial phosphoenolpyruvate: sugar phosphotransferase system (PTS)

The glucose transporter of Escherichia coli couples translocation with phos phorylation of glucose. The IICBGlc subunit spans the membrane eight times. Split, circularly permuted and cyclized forms of IICBGlc are described. Th e split variant was 30 times more active when the two proteins were encoded by a dicistronic mRNA than by two genes. The stability and activity of cir cularly permuted forms was improved when they were expressed as fusion prot eins with alkaline phosphatase. Cyclized IICBGlc and IIA(Glc), were produce d in vivo by RecA intein-mediated trans-splicing. Purified, cyclized IIA(Gl c) and IICBGlc had 100% and 30% of wild-type glucose phosphotransferase act ivity, respectively. Cyclized IIA(Glc) displayed increased stability agains t temperature and GuHCl-induced unfolding. (C) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserv ed.