Structure-function analysis of Plasmodium RNA triphosphatase and description of a triphosphate tunnel metalloenzyme superfamily that includes Cet1-like RNA triphosphatases and CYTH proteins Journal Article

   

Authors:	Gong, C.; Smith, P.; Shuman, S.
Article Title:	Structure-function analysis of Plasmodium RNA triphosphatase and description of a triphosphate tunnel metalloenzyme superfamily that includes Cet1-like RNA triphosphatases and CYTH proteins
Abstract:	RNA triphosphatase catalyzes the first step in mRNA capping. The RNA triphosphatases of fungi and protozoa are structurally and mechanistically unrelated to the analogous mammalian enzyme, a situation that recommends RNA triphosphatase as an anti-infective target. Fungal and protozoan RNA triphosphatases belong to a family of metal-dependent phosphohydrolases exemplified by yeast Cet1. The Cet1 active site is unusually complex and located within a topologically closed hydrophilic β-barrel (the triphosphate tunnel). Here we probe the active site of Plasmodium falciparum RNA triphosphatase by targeted mutagenesis and thereby identify eight residues essential for catalysis. The functional data engender an improved structural alignment in which the Plasmodium counterparts of the Cet1 tunnel strands and active-site functional groups are located with confidence. We gain insight into the evolution of the Cet1-like triphosphatase family by noting that the heretofore unique tertiary structure and active site of Cet1 are recapitulated in recently deposited structures of proteins from Pyrococcus (PBD 1YEM) and Vibrio (PDB 2ACA). The latter proteins exemplify a CYTH domain found in CyaB-like adenylate cyclases and mammalian thiamine triphosphatase. We conclude that the tunnel fold first described for Cet1 is the prototype of a larger enzyme superfamily that includes the CYTH branch. This superfamily, which we name "triphosphate tunnel metalloenzyme," is distributed widely among bacterial, archaeal, and eukaryal taxa. It is now clear that Cet1-like RNA triphosphatases did not arise de novo in unicellular eukarya in tandem with the emergence of caps as the defining feature of eukaryotic mRNA. They likely evolved by incremental changes in an ancestral tunnel enzyme that conferred specificity for RNA 5′-end processing. Published by Cold Spring Harbor Laboratory Press. Copyright © 2006 RNA Society.
Keywords:	unclassified drug; protein localization; mammalia; animals; amino acid substitution; phosphatase; microbial enzyme; rna triphosphatase; acid anhydride hydrolases; structure activity relation; structure-activity relationship; bacteria (microorganisms); rna; bacterial protein; amino acid sequence; conserved sequence; molecular sequence data; sequence homology, amino acid; rna caps; eukaryota; recombinant proteins; binding site; models, molecular; protein structure, tertiary; binding sites; protein structure; plasmodium falciparum; catalytic domain; phosphates; protein structure, secondary; mutagenesis; protozoa; fungi; archaea; pyrococcus; adenylate cyclase; peptide mapping; malaria; rna capping; manganese; protozoan proteins; protein cet1; triphosphate tunnel metalloenzyme; nucleoside-triphosphatase; metalloprotein; plasmodium; rna, protozoan; sulfates; thiamine triphosphatase; enzyme evolution; phosphohydrolase; protein cyth; protein pbd 1yem; protein pdb 2aca; residue analysis; plasmodium (apicomplexa); vibrio
Journal Title:	RNA
Volume:	12
Issue:	8
ISSN:	1355-8382
Publisher:	Cold Spring Harbor Laboratory Press
Date Published:	2006-01-01
Start Page:	1468
End Page:	1474
Language:	English
DOI:	10.1261/rna.119806
PUBMED:	16809816
PROVIDER:	scopus
PMCID:	PMC1524888
DOI/URL:	http://www.scopus.com/inward/record.url?eid=2-s2.0-33746571989&partnerID=40&md5=c421fd3cb974610bd0d30613d9698b4b
Notes:	--- - "Cited By (since 1996): 9" - "Export Date: 4 June 2012" - "CODEN: RNARF" - "Source: Scopus"

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