Unknown

Dataset Information

0

Role of loop-loop interactions in coordinating motions and enzymatic function in triosephosphate isomerase.


ABSTRACT: The enzyme triosephosphate isomerase (TIM) has been used as a model system for understanding the relationship between protein sequence, structure, and biological function. The sequence of the active site loop (loop 6) in TIM is directly correlated with a conserved motif in loop 7. Replacement of loop 7 of chicken TIM with the corresponding loop 7 sequence from an archaeal homologue caused a 10(2)-fold loss in enzymatic activity, a decrease in substrate binding affinity, and a decrease in thermal stability. Isotope exchange studies performed by one-dimensional (1)H NMR showed that the substrate-derived proton in the enzyme is more susceptible to solvent exchange for DHAP formation in the loop 7 mutant than for WT TIM. TROSY-Hahn Echo and TROSY-selected R(1rho) experiments indicate that upon mutation of loop 7, the chemical exchange rate for active site loop motion is nearly doubled and that the coordinated motion of loop 6 is reduced relative to that of the WT. Temperature dependent NMR experiments show differing activation energies for the N- and C-terminal hinges in this mutant enzyme. Together, these data suggest that interactions between loop 6 and loop 7 are necessary to provide the proper chemical context for the enzymatic reaction to occur and that the interactions play a significant role in modulating the chemical dynamics near the active site.

SUBMITTER: Wang Y 

PROVIDER: S-EPMC2713366 | biostudies-literature | 2009 Jun

REPOSITORIES: biostudies-literature

altmetric image

Publications

Role of loop-loop interactions in coordinating motions and enzymatic function in triosephosphate isomerase.

Wang Yan Y   Berlow Rebecca B RB   Loria J Patrick JP  

Biochemistry 20090601 21


The enzyme triosephosphate isomerase (TIM) has been used as a model system for understanding the relationship between protein sequence, structure, and biological function. The sequence of the active site loop (loop 6) in TIM is directly correlated with a conserved motif in loop 7. Replacement of loop 7 of chicken TIM with the corresponding loop 7 sequence from an archaeal homologue caused a 10(2)-fold loss in enzymatic activity, a decrease in substrate binding affinity, and a decrease in thermal  ...[more]

Similar Datasets

| S-EPMC2556966 | biostudies-literature
| S-EPMC4694050 | biostudies-literature
| S-EPMC3711204 | biostudies-literature
| S-EPMC3169408 | biostudies-literature
| S-EPMC140880 | biostudies-literature
| S-EPMC4051426 | biostudies-literature
| S-EPMC2890037 | biostudies-literature
| S-EPMC3787511 | biostudies-literature
| S-EPMC4748702 | biostudies-literature
| S-EPMC3926746 | biostudies-literature