Cyclooxygenase (COX2) and inducible nitric oxide synthase (iNOS) are two major inflammatory mediators. Inducible NOS specifically binds to COX2 and S-nitrosylates it, enhancing COX2 catalytic activity. Selectively disrupting iNOS--COX2 binding prevents NO-mediated activation of COX2. The synergistic molecular interaction between two inflammatory systems permits assays for developing anti-inflammatory drugs.