ON THE ROLE OF DMPK, AN AUXILIARY PROTEIN ASSOCIATED WITH MULTICOMPONENT PHENOL HYDROXYLASE FROM PSEUDOMONAS SP. STRAIN CF600

DmpK from Pseudomonas sp. strain CF600 represents a group of proteins required by phenol-degrading bacteria that utilize a multicomponent ir on-containing phenol hydroxylase, DmpK has been overexpressed in Esche richia coli and purified to homogeneity; it lacks redox cofactors and was found to strongly inhibit phenol hydroxylase in vitro, Chemical cr oss-linking experiments established that DmpK binds to the two largest subunits of the oxygenase component of the hydroxylase; this may inte rfere with binding of the hydroxylase activator protein, DmpM, causing inhibition, Since expression of DmpK normally appears to be much lowe r than that of the components of the oxygenase, inhibition may not occ ur in vivo. Hence, the interaction between DmpK and the oxygenase mani fested in the inhibition and crosslinking results prompted constructio n of E. coli strains in which the oxygenase component was expressed in the presence and absence of a low molar ratio of DmpK, Active oxygena se was detected only when expressed in the presence of DmpK, Furthermo re, inactive oxygenase could be activated in vitro by adding ferrous i ron, in a process that was dependent on the presence of DmpK, These re sults indicate that DmpK plays a role in assembly of the active form o f the oxygenase component of phenol hydroxylase.