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Crystal structure of a human hydroxymethyglutaryl‐CoA lyase (HMGCL) complex with inhibitor and divalent cation suggests the basis for substrate stereospecificity
Author(s) -
Miziorko Henry M,
Fu Zhuji,
Runquist Jennifer A,
Kim JungJa P
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a275-b
Subject(s) - chemistry , stereochemistry , ternary complex , divalent , moiety , stereospecificity , thioester , active site , molecule , crystal structure , amide , lyase , substrate (aquarium) , enzyme , phosphonate , crystallography , catalysis , biochemistry , organic chemistry , oceanography , geology
3‐(R,S)‐Hydroxyglutaryl‐CoA (HG‐CoA) has been soaked into HMGCL crystals, supporting determination of a structure (2.4 Angstrom) for the ternary enzyme‐Mg‐HG‐CoA complex. The complex contains the S‐isomer of this competitive inhibitor, reflecting binding specificity. R41's guanidinium group (catalytically important and implicated in enolization of product acetyl‐CoA) interacts with oxygens of both the C1 thioester carbonyl and C3 alcohol groups. In comparison with the structure of the enzyme‐Mg‐3‐hydroxyglutaric acid complex, Mg ligation is altered in the HMGCL‐ Mg‐HG‐CoA complex. A liganded water molecule and the N275 amide are replaced by oxygens from the C5 carboxyl and C3 hydroxyl groups of HG‐CoA. The S‐isomer of the 3‐HG moiety is required for interactions of the C3 oxygen with R41 and Mg, accounting for incorporation of (S)‐HG‐CoA into the complex as well as HMGCL specificity for the substrate (3S)‐HMG‐CoA. An ordered water molecule bridges the divalent cation and D42's carboxyl group and may participate in reaction chemistry, which is impaired by mutations that affect the enzyme‐Mg complex. The largest effects of substitutions that affect cation ligands are those that eliminate a carboxyl side chain of D42. DK21491