Cloning, functional expression, and mutational analysis of a cDNA for Lotus japonicus mitochondrial phosphate transporter

A full-length cDNA encoding mitochondrial phosphate transporter was isolated from symbiotic nodules of Lotus japonicus, a model legume. The gene appeared to be single-copied and its transcript was abundant in roots, symbiotic root nodules and shoots, in that order. The L. japonicus transporter has a conserved N-ethylmaleimide-reactive Cys residue. Site-directed mutagenesis and phosphate transport assaying in vitro showed that this Cys residue is preferable for the transport activity, although it can be replaced to some extent by Ser, but not by Ala.