Article,
Nucleotides and Mg ions differentially regulate K channels and non-selective cation channels present in cells forming the stomatal complex
Plant and Cell Physiology, 46 (10): 1682-1689 (2005)981jd Times Cited:10 Cited References Count:38.
DOI: 10.1093/pcp/pci184
Abstract
Voltage-dependent inward-rectifying (Ki(in)) and outward-rectifying (K-out) K+ channels are capable of mediating K+ fluxes across the plasma membrane. Previous studies on guard cells or heterologously expressed K+ channels provided evidence for the requirement of ATP to maintain K+ channel activity. Here, the nucleotide and Mg2+ dependencies of time-dependent Ki(in) and K-out channels from maize subsidiary cells were examined, showing that MgATP as well as MgADP function as channel activators. In addition to K-out channels, these studies revealed the presence of another outward-rectifying channel type (MgC) in the plasma membrane that however gates in a nucleotide-independent manner. MgC represents a new channel type distinguished from K-out, channels by fast activation kinetics, inhibition by elevated intracellular Mg2+ concentration, permeability for K+ as well as for Na+ and insensitivity towards TEA(+). Similar observations made for guard cells from Zea mays and Vicia faba suggest a conserved regulation of channel-mediated K+ and Na+ transport in both cell types and species.
