title: A cyanase is transcriptionally regulated by arginine and involved in cyanate decomposition in Sordaria macrospora.
abstract: Cyanase degrades toxic cyanate to NH3 and CO2 in a bicarbonate-dependent reaction. High concentrations of cyanate are fairly toxic to organisms. Here, we characterize a eukaryotic cyanase for the first time. We have isolated the cyn1 gene encoding a cyanase from the filamentous ascomycete Sordaria macrospora and functionally characterized the cyn1 product after heterologous expression in Escherichia coli. Site-directed mutagenesis confirmed a predicted catalytic centre of three conserved amino-acids. A Deltacyn1 knockout in S. macrospora was totally devoid of cyanase activity and showed an increased sensitivity to exogenously supplied cyanate in an arginine-depleted medium, defects in ascospore germination, but no other obvious morphological phenotype. By means of real-time PCR we have demonstrated that the transcriptional level of cyn1 is markedly elevated in the presence of cyanate and down-regulated by addition of arginine. The putative functions of cyanase in fungi are discussed.
authors.affiliation: Institute of Microbiology and Genetics, Department of Genetics of Eukaryotic Microorganisms, Georg-August University, Grisebachstr. 8, D-37077 Göttingen, Germany.
authors.forename: Skander
authors.initials: S
authors.lastname: Elleuche
authors.forename: Stefanie
authors.initials: S
authors.lastname: Pöggeler
mesh_terms: D000595:Amino Acid Sequence; D001120:Arginine / Q000378:metabolism*; D001203:Ascomycota / Q000145:classification / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D001673:Biodegradation, Environmental; D019759:Carbon-Nitrogen Lyases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D003485:Cyanates / Q000378:metabolism*; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D015966:Gene Expression Regulation, Fungal; D008969:Molecular Sequence Data; D010802:Phylogeny; D016415:Sequence Alignment; D014158:Transcription, Genetic
chemical_list: D003485:Cyanates; D005656:Fungal Proteins; D001120:Arginine; C019953:cyanate hydrolase; D019759:Carbon-Nitrogen Lyases