| First Author | Vecchio AJ | Year | 2012 |
| Journal | J Biol Chem | Volume | 287 |
| Issue | 29 | Pages | 24619-30 |
| PubMed ID | 22637474 | Mgi Jnum | J:192985 |
| Mgi Id | MGI:5467187 | Doi | 10.1074/jbc.M112.372243 |
| Citation | Vecchio AJ, et al. (2012) Investigating substrate promiscuity in cyclooxygenase-2: the role of Arg-120 and residues lining the hydrophobic groove. J Biol Chem 287(29):24619-30 |
| abstractText | 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. |
