Activation of the urease of Schizosaccharomyces pombe by the UreF accessory protein from soybean

Plant orthologs of the bacteria] urease accessory genes ureD and ureF, which are required for the insertion of the nickel ion at the active site, have been isolated from soybean (Glycine max L. Merr.), tomato (Lycopersicon esculentum) and Arabidopsis thaliana. The functionality of soybean UreD and UreF was tested by measuring their ability to complement urease-negative mutants of Schizosaccharomyces pombe, a eukaryote which produces a "plant-like" urease of similar to90 kDa. The S. pombe ure4 mutant was complemented by a 12-kb fragment of S. pombe genomic DNA, which was shown by PCR to contain a putative ureD gene. However, ure4 was not complemented by a UreD cDNA soybean, expressed under the control of a strong promoter. In contrast, an S. pombe ure3 mutation was complemented by both a 10-kb fragment of S. pombe DNA containing ureF and the UreF cDNA from soybean. Soybean Eu2 is a candidate urease accessory gene; its product cooperates with the Eu3 protein in activating apourease in vitro. However, the sequences of UreD and UreF transcripts from two eu2/eu2 mutants, recovered as RTPCR products, revealed no mutational alteration, suggesting that Eu2 encodes neither UreD nor UreF.