Dimeric enzyme IImtl of the E. coli phosphoenolpyruvate-dependent phosphotransferase system. Cross-linking studies with bifunctional sulfhydryl reagents.
The occurrence of intermolecular dithiols on EIImtl has been studied with a number of thiol-specific cross-linking reagents. The reaction of EIImtl with bifunctional maleimide derivatives inactivates the enzyme. At the same time the enzyme is irreversibly cross-linked to a dimeric species. Under optimal conditions 50% of the protein is cross-linked upon reaction with the dimaleimides. The enzyme is also cross-linked under oxidizing conditions in the presence of CuCl2, presumably by oxidizing an intermolecular dithiol to a disulfide. This oxidation can be reversed by the addition of the reducing agent dithiothreitol. The reaction of phosphorylated EIImtl with the same sulfhydryl-specific bifunctional reagents does not lead to any cross-linked product. The results are discussed in terms of the association state of the purified protein and the distribution of its thiol groups.
D001665:Binding Sites; D003432:Cross-Linking Reagents; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D006868:Hydrolysis; D008970:Molecular Weight; D009004:Monosaccharide Transport Proteins; D010084:Oxidation-Reduction; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism*; D011487:Protein Conformation; D013439:Sulfhydryl Reagents
D003432:Cross-Linking Reagents; D029968:Escherichia coli Proteins; D009004:Monosaccharide Transport Proteins; D013439:Sulfhydryl Reagents; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C022358:mannitol PTS permease, E coli