2Y6Z image
Entry Detail
PDB ID:
2Y6Z
Keywords:
Title:
Crystallographic structure of GM23 an example of Catalytic migration from TIM to thiamin phosphate synthase.
Biological Source:
Source Organism:
Host Organism:
PDB Version:
Deposition Date:
2011-01-27
Release Date:
2011-12-07
Method Details:
Experimental Method:
Resolution:
2.60 Å
R-Value Free:
0.23
R-Value Work:
0.19
R-Value Observed:
0.19
Space Group:
P 65 2 2
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:TRIOSE-PHOSPHATE ISOMERASE
Mutations:YES
Chain IDs:A
Chain Length:256
Number of Molecules:1
Biological Source:TRYPANOSOMA BRUCEI BRUCEI
Primary Citation
Evolutionary Walk between (Beta/Alpha)(8) Barrels: Catalytic Migration from Triosephosphate Isomerase to Thiamin Phosphate Synthase.
J.Mol.Biol. 416 255 ? (2012)
PMID: 22226942 DOI: 10.1016/J.JMB.2011.12.042

Abstact

The functionally versatile (β/α)(8) barrel scaffold was used to migrate triosephosphate isomerase (TPI) to thiamin phosphate synthase (TPS) activity, two enzymes that share the same fold but catalyze unrelated reactions through different mechanisms. The high sensitivity of the selection methodology was determinant to succeed in finding proteins with the desired activity. A combination of rational design and random mutagenesis was used to achieve the desired catalytic migration. One of the parallel directed evolution strategies followed resulted in TPI derivatives able to complement the thiamin phosphate auxotrophy phenotype of an Escherichia coli strain deleted of thiE, the gene that codes for TPS. Successive rounds of directed evolution resulted in better complementing TPI variants. Biochemical characterization of some of the evolved TPI clones demonstrated that the K(m) for the TPS substrates was similar to that of the native TPS; however and in agreement with the very slow complementation phenotype, the k(cat) was 4 orders of magnitude lower, indicating that substrate binding played a major role on selection. Interestingly, the crystal structure of the most proficient variant showed a slightly modified TPI active site occupied by a thiamin-phosphate-like molecule. Substitution of key residues in this region reduced TPS activity, strongly suggesting that this is also the catalytic site for the evolved TPS activity. The presence of the TPS reaction product at the active site explains the fast inactivation of the enzyme observed. In conclusion, by combining rational design, random mutagenesis and a very sensitive selection, it is possible to achieve enzymatic activity migration.

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