Bacterial transporters: charge translocation and mechanism.
A comparative review of the electrophysiological characterization of selected secondary active transporters from Escherichia coli is presented. In melibiose permease MelB and the Na(+)/proline carrier PutP pre-steady-state charge displacements can be assigned to an electrogenic conformational transition associated with the substrate release process. In both transporters cytoplasmic release of the sugar or the amino acid as well as release of the coupling cation are associated with a charge displacement. This suggests a common transport mechanism for both transporters. In the NhaA Na(+)/H(+) exchanger charge translocation due to its steady-state transport activity is observed. A new model is proposed for pH regulation of NhaA that is based on coupled Na(+) and H(+) equilibrium binding.
Biophysical Department, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania.
Constanta
C
Ganea
Klaus
K
Fendler
D026921:Amino Acid Transport Systems, Neutral / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D055724:Electrophysiological Phenomena; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D007700:Kinetics; D008954:Models, Biological; D011487:Protein Conformation; D017923:Sodium-Hydrogen Exchangers / Q000737:chemistry / Q000378:metabolism; D027981:Symporters / Q000737:chemistry / Q000378:metabolism
D026921:Amino Acid Transport Systems, Neutral; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; C102839:NhaA protein, E coli; D017923:Sodium-Hydrogen Exchangers; D027981:Symporters; C060609:PutP protein, E coli; C021548:melibiose permease