EVIDENCE FOR A MAGIC MAGNETIC-CONFIGURATION BETWEEN FMN AND THE [2FE-2S](+) CENTER OF PHTHALATE DIOXYGENASE REDUCTASE OF PSEUDOMONAS-CEPACIA

The enzyme phthalate dioxygenase reductase of Pseudomonas cepacia contains two prosthetic groups, a flavin mononucleotide, and a [2Fe-2S] center. Although these centers are separated by only 12 Angstrom according to the X-ray crystal structure, no magnetic coupling effects are detected on their EPR spectrum in the NADH-reduced state of the enzyme in which both centers are paramagnetic. In this paper, we demonstrate that the peculiar arrangement of the prosthetic groups together with the location of the reducible iron site gives rise to a ''magic magnetic configuration'' for which the dipolar interactions cancel.