Abstract
Methodology was developed for measurement of K+ transport in pea [Pisum sativum] cotyledon mitochondria isolated by zonal centrifugation. The valinomycin-mediated transport process required respiratory energy from Krebs cycle intermediates and was completely reversible in the absence of oxygen. The rate and extent of uptake were dependent on the presence of proton-conducting anions (with acetate plus phosphate being most effective), well-coupled mitochondria, and the K+ concentration.