title: Structure and Stability of the Dimeric Triosephosphate Isomerase from the Thermophilic Archaeon Thermoplasma acidophilum.
abstract: Thermoplasma acidophilum is a thermophilic archaeon that uses both non-phosphorylative Entner-Doudoroff (ED) pathway and Embden-Meyerhof-Parnas (EMP) pathway for glucose degradation. While triosephosphate isomerase (TPI), a well-known glycolytic enzyme, is not involved in the ED pathway in T. acidophilum, it has been considered to play an important role in the EMP pathway. Here, we report crystal structures of apo- and glycerol-3-phosphate-bound TPI from T. acidophilum (TaTPI). TaTPI adopts the canonical TIM-barrel fold with eight α-helices and parallel eight β-strands. Although TaTPI shares ~30% sequence identity to other TPIs from thermophilic species that adopt tetrameric conformation for enzymatic activity in their harsh physiological environments, TaTPI exists as a dimer in solution. We confirmed the dimeric conformation of TaTPI by analytical ultracentrifugation and size-exclusion chromatography. Helix 5 as well as helix 4 of thermostable tetrameric TPIs have been known to play crucial roles in oligomerization, forming a hydrophobic interface. However, TaTPI contains unique charged-amino acid residues in the helix 5 and adopts dimer conformation. TaTPI exhibits the apparent Td value of 74.6°C and maintains its overall structure with some changes in the secondary structure contents at extremely acidic conditions (pH 1-2). Based on our structural and biophysical analyses of TaTPI, more compact structure of the protomer with reduced length of loops and certain patches on the surface could account for the robust nature of Thermoplasma acidophilum TPI.
authors.affiliation: Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul, Korea.
authors.forename: Sang Ho
authors.initials: SH
authors.lastname: Park
authors.affiliation: Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul, Korea.
authors.forename: Hyoun Sook
authors.initials: HS
authors.lastname: Kim
authors.affiliation: Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul, Korea.
authors.forename: Mi Seul
authors.initials: MS
authors.lastname: Park
authors.affiliation: Department of Agricultural Biotechnology, Seoul National University, Seoul, Korea.
authors.forename: Sojin
authors.initials: S
authors.lastname: Moon
authors.affiliation: Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul, Korea.
authors.forename: Mi Kyung
authors.initials: MK
authors.lastname: Song
authors.affiliation: Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul, Korea.
authors.forename: Han Su
authors.initials: HS
authors.lastname: Park
authors.affiliation: Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul, Korea.
authors.forename: Hyunggu
authors.initials: H
authors.lastname: Hahn
authors.affiliation: Department of Chemistry, Mokpo National University, Chonnam, Korea.
authors.forename: Soon-Jong
authors.initials: SJ
authors.lastname: Kim
authors.affiliation: Department of Agricultural Biotechnology, Seoul National University, Seoul, Korea.
authors.forename: Euiyoung
authors.initials: E
authors.lastname: Bae
authors.affiliation: College of Pharmacy, Chung-Ang University, Seoul, Korea.
authors.forename: Hyun-Jung
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul, Korea.
authors.forename: Byung Woo
authors.initials: BW
authors.lastname: Han
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D004099:Dihydroxyacetone Phosphate / Q000737:chemistry; D019281:Dimerization; D005986:Glyceraldehyde 3-Phosphate / Q000737:chemistry / Q000378:metabolism*; D006019:Glycolysis / Q000502:physiology; D008958:Models, Molecular; D011487:Protein Conformation; D013822:Thermoplasma / Q000201:enzymology*; D014305:Triose-Phosphate Isomerase / Q000378:metabolism* / Q000648:ultrastructure*
chemical_list: D005986:Glyceraldehyde 3-Phosphate; D004099:Dihydroxyacetone Phosphate; D014305:Triose-Phosphate Isomerase