Assignment of 1H, 13C and 15N NMR signals in the toluene 4-monooxygenase effector protein.

Abstract

Toluene-4-monooxygenase (T4MO) catalyzes the NADHand O2-dependent hydroxylation of toluene to form p-cresol (Fox, 1997). T4MO belongs to an evolutionarily related family including methane monooxygenase, other aromatic monooxygenases, and alkene epoxidases. In all of these complexes, a small protein is obligately required to effect catalysis. It is reasonable to assume that the role of a diiron effector protein is to produce essential conformational changes by formation of specific protein–protein complexes. Recently, NMR structures for the effector proteins from the methane monooxygenase (MMOB) and phenol hydroxylase (P2) complexes have been reported. While MMOB has a compact fold with βαββ and βααββ domains (Chang et al., 1999; Walters et al., 1999), multiple configurations of P2 were detected in solution. This heterogeneity was postulated to reflect conformational flexibility possibly associated with catalytic function (Qian et al., 1997). Here we report chemical shift assignments for T4MOD. The solution structure of T4MOD arising from further analysis of these NMR assignments will provide a useful comparison to the NMR structures of other members of the effector protein family. Furthermore, this work provides the basis for more detailed study of the protein surface and specific residue contacts required for catalytic protein–protein interactions in the T4MO complex.