The regulatory component (MMOB) of soluble methane monooxygenase (sMMO) has a unique N-terminal tail not found in regulatory proteins of other bacterial multicomponent monooxygenases. This N-terminal tail is indispensable for proper function, yet its structure and role in catalysis remain elusive. Here we report a double electron-electron resonance (DEER) study of MMOB conformation in solution, in complex with the sMMO hydroxylase, MMOH. The results are in overall agreement with the previously reported crystal structure. In the solution state, however, the N-terminal tail of MMOB is in a more relaxed, flexible state, suggesting fewer H-bonding interactions than found in the crystal. Upon reduction of MMOH from the diiron(III) to the diiron(II) form, the MMOB tail becomes significantly more ordered. The observed conformational change is consistent with higher binding affinity of MMOB to MMOH in the diiron(II) state, which may allow MMOB more readily to displace the reductase component (MMOR) from MMOH after reduction, and exert its regulatory effect by both the core and the N-terminal tail, priming the reduced MMOH-2MMOB complex for catalysis.  This work was supported by a grant from the National Institute of General Medical Sciences.

Conformational modulation of the regulatory component of soluble methane monooxygenase by the oxidation state of the hydroxylase

247th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.