3TZI: X-ray crystal structure of arachidonic acid bound in the cyclooxygenase channel of G533V murine COX-2

Citation:
Abstract
The cyclooxygenases (COX-1 and COX-2) generate prostaglandin H(2) from arachidonic acid (AA). In its catalytically productive conformation, AA binds within the cyclooxygenase channel with its carboxylate near Arg-120 and Tyr-355 and omega-end located within a hydrophobic groove above Ser-530. Although AA is the preferred substrate for both isoforms, COX-2 can oxygenate a broad spectrum of substrates. Mutational analyses have established that an interaction of the carboxylate of AA with Arg-120 is required for high affinity binding by COX-1 but not COX-2, suggesting that hydrophobic interactions between the omega-end of substrates and cyclooxygenase channel residues play a significant role in COX-2-mediated oxygenation. We used structure-function analyses to investigate the role that Arg-120 and residues lining the hydrophobic groove play in the binding and oxygenation of substrates by murine (mu) COX-2. Mutations to individual amino acids within the hydrophobic groove exhibited decreased rates of oxygenation toward AA with little effect on binding. R120A muCOX-2 oxygenated 18-carbon omega-6 and omega-3 substrates albeit at reduced rates, indicating that an interaction with Arg-120 is not required for catalysis. Structural determinations of Co(3+)-protoporphyrin IX-reconstituted muCOX-2 with alpha-linolenic acid and G533V muCOX-2 with AA indicate that proper bisallylic carbon alignment is the major determinant for efficient substrate oxygenation by COX-2. Overall, these findings implicate Arg-120 and hydrophobic groove residues as determinants that govern proper alignment of the bisallylic carbon below Tyr-385 for catalysis in COX-2 and confirm nuances between COX isoforms that explain substrate promiscuity.
PDB ID: 3TZIDownload
MMDB ID: 98984
PDB Deposition Date: 2011/9/27
Updated in MMDB: 2017/11
Experimental Method:
x-ray diffraction
Resolution: 2.15  Å
Source Organism:
Similar Structures:
Biological Unit for 3TZI: dimeric; determined by author and by software (PISA)
Molecular Components in 3TZI
Label Count Molecule
Proteins (2 molecules)
2
Prostaglandin G/H Synthase 2(Gene symbol: Ptgs2)
Molecule annotation
Chemicals (26 molecules)
1
2
2
2
3
10
4
1
5
1
6
8
7
2
* Click molecule labels to explore molecular sequence information.

Citing MMDB
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