1b78
STRUCTURE-BASED IDENTIFICATION OF THE BIOCHEMICAL FUNCTION OF A HYPOTHETICAL PROTEIN FROM METHANOCOCCUS JANNASCHII:MJ0226
Structural highlights
FunctionIXTPA_METJA Pyrophosphatase that catalyzes the hydrolysis of nucleoside triphosphates to their monophosphate derivatives, with a high preference for the non-canonical purine nucleotides xanthosine triphosphate (XTP), deoxyinosine triphosphate (dITP) and ITP (PubMed:10404228, PubMed:11452035). Probably functions as a house-cleaning enzyme that removes non-canonical purine nucleotides from the nucleotide pool, thus preventing their incorporation into DNA/RNA and avoiding chromosomal lesions (PubMed:11452035). Shows very low activity on GTP or dGTP, both of which are hydrolyzed more than 100-fold less efficiently than XTP, and has nearly no activity toward the canonical nucleotides ATP, CTP, and TTP, and toward 6-N-hydroxylaminopurine deoxynucleoside triphosphate (dHAPTP) (PubMed:10404228, PubMed:11452035). Displays neither endonuclease nor 3'-exonuclease activities (PubMed:11452035).[1] [2] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedAlmost half of the entire set of predicted genomic products from Methanococcus jannaschii are classified as functionally unknown hypothetical proteins. We present a structure-based identification of the biochemical function of a protein with an as yet unknown function from a M. jannaschii gene, Mj0226. The crystal structure of Mj0226 protein determined at 2.2 A resolution reveals that the protein is a homodimer and each monomer folds into an elongated alpha/beta structure of a new fold family. Comparisons of Mj0226 protein with protein structures in the database, however, indicate that one part of the protein is homologous to some of the nucleotide-binding proteins. Biochemical analysis shows that Mj0226 protein is a novel nucleotide triphosphatase that can efficiently hydrolyze nonstandard nucleotides such as XTP to XMP or ITP to IMP, but not the standard nucleotides, in the presence of Mg2+ or Mn2+ ions. Structure-based identification of a novel NTPase from Methanococcus jannaschii.,Hwang KY, Chung JH, Kim SH, Han YS, Cho Y Nat Struct Biol. 1999 Jul;6(7):691-6. PMID:10404228[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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