Human Δ3, Δ2‐enoyl‐CoA isomerase, type 2: a structural enzymology study on the catalytic role of its ACBP domain and helix‐10. (14th January 2015)

• Record Type: Journal Article
• Authors: Onwukwe, Goodluck U.; Kursula, Petri; Koski, M. Kristian; Schmitz, Werner; Wierenga, Rik K.
• Is Part Of: FEBS journal. Volume 282:Number 4(2015)
• Page Start: 746
• Page End: 768
• Publication Date: 2015-01-14
• Subjects: Biochemistry -- Periodicals; Molecular biology -- Periodicals; Pathology, Molecular -- Periodicals; 572
• DOI: 10.1111/febs.13179
• Languages: English
• ISSNs: 1742-464X

Abstract

<abstract abstract-type="main" id="febs13179-abs-0001"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="febs13179-sec-0001" sec-type="section"> <p>The catalytic domain of the trimeric human Δ<sup>3</sup>, Δ<sup>2</sup>‐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 β‐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.</p> </sec> <sec id="febs13179-sec-0002" sec-type="section"> <title>Database</title> <p>Structural data are available in the PDB database under the accession numbers <ext-link ext-link-type="uri" xlink:href="http://www.rcsb.org/pdb/search/structidSearch.do?structureId=4U18" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink">4U18</ext-link> (ISO‐ECI2), <ext-link ext-link-type="uri" xlink:href="http://www.rcsb.org/pdb/search/structidSearch.do?structureId=4U19" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink">4U19</ext-link> (ISOA‐ECI2), <ext-link ext-link-type="uri" xlink:href="http://www.rcsb.org/pdb/search/structidSearch.do?structureId=4U1A" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink">4U1A</ext-link> (ISOB‐ECI2)</p> </sec> </abstract>