Structure of the ATP-driven methyl-coenzyme M reductase activation complex

Area of Science:

• Biochemistry
• Microbiology
• Structural Biology

Background:

• Methyl-coenzyme M reductase (MCR) catalyzes methane formation, a vital biological process.
• The active site cofactor, coenzyme F430, requires nickel in the Ni(I) state for activity.
• The reductive activation mechanism of F430 within MCR is poorly understood.

Purpose of the Study:

• To investigate the mechanism of MCR activation in methanogenic archaea.
• To characterize the MCR activation complex and its components.
• To elucidate the structural basis of F430 reductive activation.

Main Methods:

• Purification and characterization of the MCR activation complex from Methanococcus maripaludis.
• In vitro functional assays demonstrating ATP-dependent MCR activation.
• Cryo-electron microscopy (cryo-EM) for structural determination.
• Topology and electron paramagnetic resonance (EPR) spectroscopy.

Main Results:

• Identified an MCR activation complex involving McrC and other proteins.
• Demonstrated strict ATP dependence for MCR activation in vitro.
• Determined cryo-EM structures of the complex at high resolution (1.8-2.1 Å).
• Revealed three complex iron-sulfur clusters forming an electron transfer pathway to F430.

Conclusions:

• The MCR activation complex facilitates the reductive activation of F430.
• The identified iron-sulfur clusters resemble nitrogenase maturation intermediates, suggesting evolutionary links.
• Provides mechanistic insights into MCR function and the evolution of ancient enzymes.