The importance of the conserved Arg191-Asp227 salt bridge of triosephosphate isomerase for folding, stability, and catalysis.
Triosephosphate isomerase (TIM) has a conserved salt bridge 20 A away from both the active site and the dimer interface. In this study, four salt bridge mutants of Trypanosoma brucei brucei TIM were characterized. The folding and stability of the mutants are impaired compared to the wild-type enzyme. This salt bridge is part of a hydrogen bonding network which tethers the C-terminal beta7alpha7beta8alpha8 unit to the bulk of the protein. In the variants D227N, D227A, and R191S, this network is preserved, as can be deduced from the structure of the R191S variant. In the R191A variant, the side chain at position 191 cannot contribute to this network. Also the catalytic power of this variant is most affected.
Kursula
Inari
I
Department of Biochemistry and Biocenter Oulu, University of Oulu, P.O. Box 3000, FIN-90014 Oulu, Finland.
Partanen
Sanna
S
Lambeir
Anne Marie
AM
Wierenga
Rik K
RK
D000818:Animals; D001120:Arginine / Q000235:genetics / Q000502:physiology*; D001224:Aspartic Acid / Q000235:genetics / Q000502:physiology*; D001665:Binding Sites; D002384:Catalysis; D017124:Conserved Sequence; D004795:Enzyme Stability; D006860:Hydrogen Bonding; D007700:Kinetics; D008956:Models, Chemical; D008958:Models, Molecular; D009154:Mutation; D017510:Protein Folding; D012492:Salts / Q000737:chemistry; D014305:Triose-Phosphate Isomerase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D014346:Trypanosoma brucei brucei / Q000201:enzymology*
D012492:Salts; D001224:Aspartic Acid; D001120:Arginine; D014305:Triose-Phosphate Isomerase