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Human Δ3, D2-enoyl-CoA isomerase, type 2: a structural enzymology study on the catalytic role ot its ACBP domain and helix-10

DOI: 10.1111/febs.13179 DOI Help
PMID: 25515061 PMID Help

Authors: Goodluck Uzodinma Onwukwe (University of Oulu) , Inari Kursula (University of Bergen) , M. Kristian Koski (University of Oulu) , Werner Schmitz (University of Wuerzberg) , Rikkert Wierenga (University of Oulu)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Febs Journal , VOL 282 (4) , PAGES 746 - 768

State: Published (Approved)
Published: February 2015

Abstract: The catalytic domain of the trimeric human D3,D2-enoyl-CoA isomerase, type 2 (HsECI2), has the typical crotonase fold. In the active site of this fold two main chain NH groups form an oxyanion hole for binding the thioester oxygen of the 3E- or 3Z-enoyl-CoA substrate molecules. A catalytic glutamate is essential for the proton transfer between the substrate C2 and C4 atoms for forming the product 2E-enoyl-CoA, which is a key intermediate in the b-oxidation pathway. The active site is covered by the C-terminal helix-10. In HsECI2, the isomerase domain is extended at its N terminus by an acyl-CoA binding protein (ACBP) domain. Small angle X-ray scattering analysis of HsECI2 shows that the ACBP domain protrudes out of the central isomerase trimer. X-ray crystallography of the isomerase domain trimer identifies the active site geometry. A tunnel, shaped by loop-2 and extending from the catalytic site to bulk solvent, suggests a likely mode of binding of the fatty acyl chains. Calorimetry data show that the separately expressed ACBP and isomerase domains bind tightly to fatty acyl-CoA molecules. The truncated isomerase variant (without ACBP domain) has significant enoyl-CoA isomerase activity; however, the full-length isomerase is more efficient. Structural enzymological studies of helix-10 variants show the importance of this helix for efficient catalysis. Its hydrophobic side chains, together with residues from loop-2 and loop-4, complete a hydrophobic cluster that covers the active site, thereby fixing the thioester moiety in a mode of binding competent for efficient catalysis.

Journal Keywords: Crotonase; Eci; Helix-10; Oxyanion Hole; Saxs

Subject Areas: Biology and Bio-materials, Chemistry

Instruments: I03-Macromolecular Crystallography

Other Facilities: MAXlab; DESY; ESRF