Structural and genomic organization, cDNA characterization and expression analysis of the urate oxidase gene from chickpea (Cicer arietinum)^†

Abstract

A complete cDNA and a genomic DNA fragment coding for urate oxidase (urate: oxygen oxidoreductase, EC 1.7.3.3) from chickpea (Cicer arietinum L.) were isolated and characterized. The 1032 bp cDNA (CAUR1) contains a complete open reading frame that encodes a 308 amino acid protein with a predicted size of 34.06 kDa and a pI of 9.38. This protein shows a strong similarity with other uricases present in the databases. Heterologous expression in Escherichia coli showed urate oxidase activity in crude extracts from induced cells, demonstrating that CAUR1 encodes a complete and functional uricase enzyme. Kinetic properties of the recom-binant enzyme were similar to those of the native uricase purified from chickpea leaves. The genomic organization of the chickpea uricase gene (CAUR1) remarkably resembles that of the soybean (Glycine max L.) uricase gene, presenting eight exons and seven introns. Within the 5 0 -flanking region of the chickpea gene, nucleotide sequences matching consensus motifs of soybean nodule NAT2-nuclear factors and common bean (Phaseolus vulgaris L.) proteins (PNF1) are present. It demonstrates that a single copy of the uricase gene is present in the chickpea genome and that the gene is expressed not only in nodules, but also in leaves and roots.

Update on ureide degradation in legumes

“…Although the gene encoding uricase has been studied at the molecular level in several legumes, very little is known about its regulatory mechanisms (Nguyen et al, 1985;Sánchez et al, 1987), and only the genomic structure and the promoter region of the gene from soybean (Nguyen et al, 1985;Takane et al, 1997) and chickpea (Redondo-Nevado et al, 2004) have been described. As expected from purification data, this gene is also expressed in organs other than nodules (Capote-Maínez and Sánchez, 1997;Redondo-Nevado et al, 2004).…”