1L8S: CARBOXYLIC ESTER HYDROLASE COMPLEX (DIMERIC PLA2 + LPC-ether + ACETATE + PHOSPHATE IONS)

Citation:
Abstract
We have solved the 1.55 A crystal structure of the anion-assisted dimer of porcine pancreatic group IB phospholipase A2 (PLA2), complexed with the products of hydrolysis of the substrate platelet activating factor. The dimer contains five coplanar phosphate anions bound at the contact surface between the two PLA2 subunits. This structure parallels a previously reported anion-assisted dimer that mimics the tetrahedral intermediate of PLA2 bound to a substrate interface [Pan, Y. H., et al. (2001) Biochemistry 40, 609-617]. The dimer structure has a molecule of the product acetate bound in subunit A and the other product 1-octadecyl-sn-glycero-3-phosphocholine (LPC-ether) to subunit B. Therefore, this structure is of the two individual product binary complexes and not of a ternary complex with both products in one active site of PLA2. Protein crystals with bound products were only obtained by cocrystallization starting from the initial substrate. In contrast, an alternate crystal form was obtained when PLA2 was cocrystallized with LPC-ether and succinate, and this crystal form did not contain bound products. The product bound structure has acetate positioned in the catalytic site of subunit A such that one of its oxygen atoms is located 3.5 A from the catalytic calcium. Likewise, a longer than typical Ca-to-Gly(32) carbonyl distance of 3.4 A results in a final Ca coordination that is four-coordinate and has distorted geometry. The other oxygen of acetate makes hydrogen bonds with N(delta)(1)-His(48), O(delta)(1)-Asp(49), and the catalytic assisting water (w7). In contrast, the glycerophosphocholine headgroup of LPC-ether in subunit B makes no contacts with calcium or with the catalytic residues His(48) or Asp(49). The tail of the LPC-ether is located near the active site pocket with the last nine carbons of the sn-1- acyl chain refined in two alternate conformations. The remaining atoms of the LPC-ether product have been modeled into the solvent channel but have their occupancies set to zero in the refined model due to disorder. Together, the crystallographic and equilibrium binding results with the two products show that the simultaneous binding of both the products in a single active site is not favored.
PDB ID: 1L8SDownload
MMDB ID: 21401
PDB Deposition Date: 2002/3/21
Updated in MMDB: 2012/12
Experimental Method:
x-ray diffraction
Resolution: 1.55  Å
Source Organism:
Similar Structures:
Biological Unit for 1L8S: dimeric; determined by author and by software (PISA)
Molecular Components in 1L8S
Label Count Molecule
Proteins (2 molecules)
2
Phospholipase A2, Major Isoenzyme(Gene symbol: PLA2G1B)
Molecule annotation
Chemicals (10 molecules)
1
2
2
1
3
5
4
1
5
1
* Click molecule labels to explore molecular sequence information.

Citing MMDB
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