title: A novel member of the YchN-like fold: solution structure of the hypothetical protein Tm0979 from Thermotoga maritima.
abstract: We report herein the NMR structure of Tm0979, a structural proteomics target from Thermotoga maritima. The Tm0979 fold consists of four beta/alpha units, which form a central parallel beta-sheet with strand order 1234. The first three helices pack toward one face of the sheet and the fourth helix packs against the other face. The protein forms a dimer by adjacent parallel packing of the fourth helices sandwiched between the two beta-sheets. This fold is very interesting from several points of view. First, it represents the first structure determination for the DsrH family of conserved hypothetical proteins, which are involved in oxidation of intracellular sulfur but have no defined molecular function. Based on structure and sequence analysis, possible functions are discussed. Second, the fold of Tm0979 most closely resembles YchN-like folds; however the proteins that adopt these folds differ in secondary structural elements and quaternary structure. Comparison of these proteins provides insight into possible mechanisms of evolution of quaternary structure through a simple mechanism of hydrophobicity-changing mutations of one or two residues. Third, the Tm0979 fold is found to be similar to flavodoxin-like folds and beta/alpha barrel proteins, and may provide a link between these very abundant folds and putative ancestral half-barrel proteins.
authors.affiliation: Guelph-Waterloo Centre for Graduate Studies in Chemistry and Biochemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Joe A
authors.initials: JA
authors.lastname: Gaspar
authors.forename: Chengsong
authors.initials: C
authors.lastname: Liu
authors.forename: Kenrick A
authors.initials: KA
authors.lastname: Vassall
authors.forename: Gabriela
authors.initials: G
authors.lastname: Meglei
authors.forename: Ricardo
authors.initials: R
authors.lastname: Stephen
authors.forename: Peter B
authors.initials: PB
authors.lastname: Stathopulos
authors.forename: Antonio
authors.initials: A
authors.lastname: Pineda-Lucena
authors.forename: Bin
authors.initials: B
authors.lastname: Wu
authors.forename: Adelinda
authors.initials: A
authors.lastname: Yee
authors.forename: Cheryl H
authors.initials: CH
authors.lastname: Arrowsmith
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Meiering
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D018360:Crystallography, X-Ray; D019281:Dimerization; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D017510:Protein Folding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry; D040901:Proteomics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012996:Solutions / Q000737:chemistry; D020124:Thermotoga maritima / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D021122:Protein Subunits; D012996:Solutions