Charge transfer in P-type ATPases investigated on planar membranes.
Planar lipid bilayers, e.g., black lipid membranes (BLM) and solid supported membranes (SSM), have been employed to investigate charge movements during the reaction cycle of P-type ATPases. The BLM/SSM method allows a direct measurement of the electrical currents generated by the cation transporter following chemical activation by a substrate concentration jump. The electrical current transients provides information about the reaction mechanism of the enzyme. In particular, the BLM/SSM technique allows identification of electrogenic steps which in turn may be used to localize ion translocation during the reaction cycle of the pump. In addition, using the high time resolution of the technique, especially when rapid activation via caged ATP is employed, rate constants of electrogenic and electroneutral steps can be determined. In the present review, we will discuss the main results obtained by the BLM and SSM methods and how they have contributed to unravel the transport mechanism of P-type ATPases.
Tadini-Buoninsegni
Francesco
F
Department of Chemistry, University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy. francesco.tadini@unifi.it
Bartolommei
Gianluca
G
Moncelli
Maria Rosa
MR
Fendler
Klaus
K
D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000502:physiology; D000818:Animals; D000252:Calcium-Transporting ATPases / Q000737:chemistry / Q000502:physiology*; D027682:Cation Transport Proteins / Q000737:chemistry / Q000502:physiology; D004560:Electricity; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000502:physiology; D017506:H(+)-K(+)-Exchanging ATPase / Q000737:chemistry / Q000502:physiology*; D006801:Humans; D017136:Ion Transport; D008051:Lipid Bilayers / Q000737:chemistry*; D012519:Sarcoplasmic Reticulum / Q000201:enzymology; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry / Q000502:physiology*
D027682:Cation Transport Proteins; D029968:Escherichia coli Proteins; D008051:Lipid Bilayers; D000251:Adenosine Triphosphatases; C058166:potassium translocating Kdp-ATPase, E coli; D017506:H(+)-K(+)-Exchanging ATPase; D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase