Sodium-dependent isoleucine transport in the methanogenic archaebacterium Methanococcus voltae

Methanococcus voltae possesses a Na +-dependent transport system for isoleucine which requires for optimum rates a CO 2/H 2 atmosphere. The K m for the system is 4.5 μM with a V max of 1.5 nmol·min −1·mg dry wt −1. Approximately 75% of the label can be released from the cell pool following short-term experiments with gradients of isoleucine reaching 100 (in/out). Transport is inhibited by ionophores and N-ethyl maleimide. Only valine and leucine effectively compete with isoleucine for transport.