Mannitol-Specific Carrier Protein from the Escherichia coli Phosphoenolpyruvate-Dependent Phosphotransferase System Can Be Extracted as a Dimer from the Membrane

摘要: The association state of the mannitol-specific enzyme II (EIIMtl) has been studied both in purified form and embedded cytoplasmic membrane. Membrane fragments obtained from mannitol-grown Escherichia coli catalyze phosphoenolpyruvate- (PEP) dependent phosphorylation glucose mannitol; thus they contain glucose- enzymes II. autoradiogram an electrophoresed mixture [32P]PEP, EI, HPr, membrane shows bands at 58 116 kilodaltons, addition to P-EI P-HPr. In analogous experiment with EIIMtl, suspended detergent micelles, only a 000-dalton band P-HPr were found. Treatment phosphorylated membranes mannitol results immediate substantial decrease radioactivity 58- 116-kilodalton bands. A similar treatment had no direct effect on autoradiogram. We conclude therefore that originate IIMtl monomers dimers, respectively. interaction between subunits dimer is not abolished by up 5% sodium dodecyl sulfate. However, nonionic Lubrol PX, which present during purification capable transforming dimers into monomers.