A high conductance cationic channel from Phaseolus vulgaris roots incorporated into planar lipid bilayers.
A previously undescribed plasma membrane cation channel from Phaseolus vulgaris bean roots was studied after its incorporation into planar lipid bilayers. The channel allows the passage of monovalent cations excluding the flux of both anions (Cl-) and divalent cations (Ca2+). The channel presents a high ( approximately 213 pS) conductance in (300 mM Kcis+)/ (150 mMKtrans+) conditions. The probability of opening (Po) is low at all the tested voltages, but it increases significantly at trans-negative potentials. Permeability ratios (Pcation/PK+) under bi-ionic conditions follow the sequence: K+ (1.0)>NH4+ (0.86)>Na+ (0.78). Under the same conditions, the conductance ratios (gamma cation/gamma K+) follow the sequence: NH4+ (1.1) > or = K+ (1.0)>Na+ (0.80). The low probability of opening exhibited by the channel upon its incorporation into a lipid bilayer makes it a candidate to regulation by (and therefore participation in) cellular signalling networks.
Balleza
Daniel
D
Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, UNAM, Ap. Postal 510-3, Cuernavaca, Morelos 62210, Mexico.
Gómez-Lagunas
Froylán
F
Sánchez
Federico
F
Quinto
Carmen
C
D002118:Calcium / Q000737:chemistry*; D002412:Cations; D004553:Electric Conductivity; D015640:Ion Channel Gating; D007473:Ion Channels / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D008564:Membrane Potentials; D027805:Phaseolus / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism*; D011188:Potassium / Q000737:chemistry*; D012964:Sodium / Q000737:chemistry*
D002412:Cations; D007473:Ion Channels; D008051:Lipid Bilayers; D012964:Sodium; D011188:Potassium; D002118:Calcium