title: Structure-based protein engineering efforts with a monomeric TIM variant: the importance of a single point mutation for generating an active site with suitable binding properties.
abstract: A monomeric variant of triosephosphate isomerase (TIM) with a new engineered binding groove has been characterized further. In this variant (ml8bTIM), the phosphate binding loop had been shortened, causing the binding site to be much more extended. Here, it is reported that in the V233A variant of ml8bTIM (A-TIM), three important properties of the wild-type TIM active site have been restored: (i) the structural properties of loop-7, (ii) the binding site of a conserved water molecule between loop-7 and loop-8 and (iii) the binding site of the phosphate moiety. It is shown that the active site of A-TIM can bind TIM transition state analogs and suicide inhibitors competently. It is found that the active site geometry of the A-TIM complexes is less compact and more solvent exposed, as in wild-type TIM. This correlates with the observation that the catalytic efficiency of A-TIM for interconverting the TIM substrates is too low to be detected. It is also shown that the A-TIM active site can bind compounds which do not bind to wild-type TIM and which are completely different from the normal TIM substrate, like a citrate molecule. The binding of this citrate molecule is stabilized by hydrogen bonding interactions with the new binding groove.
authors.affiliation: Biocenter Oulu, University of Oulu, Oulu, Finland..
authors.forename: Markus
authors.initials: M
authors.lastname: Alahuhta
authors.forename: Mikko
authors.initials: M
authors.lastname: Salin
authors.forename: Marco G
authors.initials: MG
authors.lastname: Casteleijn
authors.forename: Christian
authors.initials: C
authors.lastname: Kemmer
authors.forename: Ibrahim
authors.initials: I
authors.lastname: El-Sayed
authors.forename: Koen
authors.initials: K
authors.lastname: Augustyns
authors.forename: Peter
authors.initials: P
authors.lastname: Neubauer
authors.forename: Rik K
authors.initials: RK
authors.lastname: Wierenga
mesh_terms: D000096:Acetone / Q000031:analogs & derivatives / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D002384:Catalysis; D019343:Citric Acid / Q000737:chemistry / Q000378:metabolism; D018360:Crystallography, X-Ray; D018698:Glutamic Acid; D008958:Models, Molecular; D050505:Mutant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017354:Point Mutation; D020641:Polymorphism, Single Nucleotide; D011485:Protein Binding / Q000235:genetics; D011487:Protein Conformation; D015202:Protein Engineering / Q000379:methods*; D014305:Triose-Phosphate Isomerase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism
chemical_list: D050505:Mutant Proteins; D000096:Acetone; C002417:bromohydroxyacetone phosphate; D019343:Citric Acid; D018698:Glutamic Acid; D014305:Triose-Phosphate Isomerase