The structure of YqeH. An AtNOS1/AtNOA1 ortholog that couples GTP hydrolysis to molecular recognition.
Publication Type:Journal Article
Source:J Biol Chem, Volume 283, Issue 47, p.32968-76 (2008)
Keywords:Amino Acid Motifs, Arabidopsis Proteins, Bacillus, Cloning, Molecular, Crystallography, X-Ray, GTP Phosphohydrolases, Guanosine Triphosphate, Hydrolysis, Models, Molecular, Molecular Conformation, Nitric Oxide, Nitric Oxide Synthase, Protein Conformation, Protein Structure, Secondary, Protein Structure, Tertiary
<p>AtNOS1/AtNOA1 was identified as a nitric oxide-generating enzyme in plants, but that function has recently been questioned. To resolve issues surrounding AtNOA1 activity, we report the biochemical properties and a 2.36 A resolution crystal structure of a bacterial AtNOA1 ortholog (YqeH). Geobacillus YqeH fused to a putative AtNOA1 leader peptide complements growth and morphological defects of Atnoa1 mutant plants. YqeH does not synthesize nitric oxide from L-arginine but rather hydrolyzes GTP. The YqeH structure reveals a circularly permuted GTPase domain and an unusual C-terminal beta-domain. A small N-terminal domain, disordered in the structure, binds zinc. Structural homology among the C-terminal domain, the RNA-binding regulator TRAP, and the hypoxia factor pVHL define a recognition module for peptides and nucleic acids. TRAP residues important for RNA binding are conserved by the YqeH C-terminal domain, whose positioning is coupled to GTP hydrolysis. YqeH and AtNOA1 probably act as G-proteins that regulate nucleic acid recognition and not as nitric-oxide synthases.</p>