Is HCO3− transport in anabaena a Na+ symport?

Abstract

Na+ strongly promoted HCO3− transport in Anabaena variabilis, The effect was highly specific to this cation. Kinetic analysis indicated a progressive decrease in the Km (HCO3−) of the transport system with increasing Na+ concentration. Vmax was also affected. We raise the possibility that the transport is a Na+-HCO3− symport; alternatively, that a Na+-H+ antiport (or Na+-OH+ symport) system mediates the efflux of the OH− ions derived from the entering HCO3− ions, and that this antiport can rate-limit HCO3− influx.