Clonging, Characterization, Polygenetic Analysis And Tissue-specific Expression Of A Urease Accessory Protein Gene UreG From The Amphioxus Branchiostoma Belcheri

Amphioxus or lancelet, a cephalochordate, has long been regarded as the living invertebrate most closely related to the proximate invertebrate ancestor of vertebrates. It has been recognized as the most important model animal to analyze the origin and evolution of vertebrates. Study on the gene structure, function and expression in amphioxus will greatly contribute to the origin and evolution of the vertebrates.Urease(E.C. 3.5.1.5)is a nickel-containing enzyme catalyzing the hydrolysis of urea to form ammonia and carbon dioxide. Its activity has been found in bacteria, eukaryotic microorganisms, plants and some invertebrates. Biochemically, bacterial ureases are best characterized, and their activation requires the presence of several accessory proteins including UreD, UreE, UreF and UreG. Of the four urease accessory proteins, UreG is the most highly conserved and the only one of this group that exhibits clear sequence homology to other proteins. The presence of this putative nucleotide-binding site in UreG might be related to the in vivo energy requirement for urease activation.In the course of a large scale sequencing of amphioxus B. belcheri gut cDNA library, we have identified a clone, L239 (GenBank accession number: AAT39417), exhibiting high similarity to UreG genes. It is 966 bps long, its longest open reading frame consisting of 603 bps codes for a protein of 200 amino acid residues with a predicted molecular weight of about 22.41 kDa and an isoelectric point of 6.6. The 5'-untranslated region (UTR) is 284 bps long with a typical oligopyrimidine motif and an...