Identification and localization of the sod2 gene product in fission yeast.

Sod2, the Na+/H+ antiporter of the fission yeast Schizosaccharomyces pombe, was identified by addition of a hemagglutinin tag to the carboxyl terminus of the protein. The tagged protein was expressed in the sod2-deficient strain of S. pombe. Transformants retained tolerance to lithium (1-10 mM) at external pH values from 3.5 to 6.5. Both Na+-dependent proton uptake and active sodium extrusion were also restored in transformed cells, suggesting that a functional antiporter was present. The protein was present in a membrane fraction. In SDS PAGE it migrated as a single 47 kDa band. The protein could be efficiently solubilized with the non-ionic detergent, dodecyl maltoside. Immunofluorescent microscopy revealed an asymmetric distribution with preferable accumulation in polar tip areas. The results are the first identification and localization of the Na+/H+ exchanger in yeast cells.