title: Structural and thermodynamic folding characterization of triosephosphate isomerases from Trichomonas vaginalis reveals the role of destabilizing mutations following gene duplication.
abstract: We report the structures and thermodynamic analysis of the unfolding of two triosephosphate isomerases (TvTIM1 and TvTIM2) from Trichomonas vaginalis. Both isoforms differ by the character of four amino acids: E/Q 18, I/V 24, I/V 45, and P/A 239. Despite the high sequence and structural similarities between both isoforms, they display substantial differences in their stabilities. TvTIM1 (E18, I24, I45, and P239) is more stable and less dissociable than TvTIM2 (Q18, V24, V45, and A239). We postulate that the identities of residues 24 and 45 are responsible for the differences in monomer stability and dimer dissociability, respectively. The structural difference between both amino acids is one methyl group. In TvTIMs, residue 24 is involved in packing α-helix 1 against α-helix 2 of each monomer and residue 45 is located at the center of the dimer interface forming a "ball and socket" interplay with a hydrophobic cavity. The mutation of valine at position 45 for an alanine in TvTIM2 produces a protein that migrates as a monomer by gel filtration. A comparison with known TIM structures indicates that this kind of interplay is a conserved feature that stabilizes dimeric TIM structures. In addition, TvTIMs are located in the cytoplasm and in the membrane. As TvTIM2 is an easily dissociable dimer, the dual localization of TvTIMs may be related to the acquisition of a moonlighting activity of monomeric TvTIM2. To our knowledge, this is the simplest example of how a single amino acid substitution can provide alternative function to a TIM barrel protein.
authors.affiliation: IPICYT, División de Biología Molecular, Camino a la Presa San José 2055, San Luis Potosí, San Luis Potosí, México, CP 78216.
authors.forename: Samuel
authors.initials: S
authors.lastname: Lara-González
authors.forename: Priscila
authors.initials: P
authors.lastname: Estrella-Hernández
authors.forename: Adrián
authors.initials: A
authors.lastname: Ochoa-Leyva
authors.forename: María
authors.initials: M
authors.lastname: Del Carmen Portillo-Téllez
authors.forename: Luis A
authors.initials: LA
authors.lastname: Caro-Gómez
authors.forename: Elisa E
authors.initials: EE
authors.lastname: Figueroa-Angulo
authors.forename: Holjes
authors.initials: H
authors.lastname: Salgado-Lugo
authors.forename: Jesús F T
authors.initials: JF
authors.lastname: Miranda Ozuna
authors.forename: Jaime
authors.initials: J
authors.lastname: Ortega-López
authors.forename: Rossana
authors.initials: R
authors.lastname: Arroyo
authors.forename: Luis G
authors.initials: LG
authors.lastname: Brieba
authors.forename: Claudia G
authors.initials: CG
authors.lastname: Benítez-Cardoza
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D002850:Chromatography, Gel; D002942:Circular Dichroism; D003460:Crystallization; D017931:DNA Primers / Q000235:genetics; D019281:Dimerization; D019084:Fluorescent Antibody Technique, Indirect; D020440:Gene Duplication / Q000235:genetics*; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics*; D011487:Protein Conformation; D017510:Protein Folding; D055550:Protein Stability; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics; D014246:Trichomonas vaginalis / Q000201:enzymology*; D014305:Triose-Phosphate Isomerase / Q000737:chemistry* / Q000235:genetics
chemical_list: D017931:DNA Primers; D007527:Isoenzymes; D014305:Triose-Phosphate Isomerase
keywords: TIM barrel; crystal structures; monomer association; moonlighting protein; thermodynamic analysis of the unfolding