A minimal SufB₂C₂ complex functions as a [4Fe-4S] cluster scaffold in methanogenic archaea

Area of Science:

• Biochemistry
• Microbiology
• Evolutionary Biology

Background:

• Iron-sulfur (Fe-S) clusters are vital cofactors across all life forms.
• Their biogenesis in obligate anaerobic archaea is not well understood.
• Methanogenic archaea possess a simplified Fe-S cluster assembly system.

Purpose of the Study:

• To characterize the minimal two-protein SUF system (SufB and SufC) in methanogenic archaea.
• To elucidate the mechanism of Fe-S cluster binding and transfer.
• To explore the evolutionary origins of Fe-S cluster biogenesis.

Main Methods:

• Utilized *Methanococcus maripaludis* as a model organism.
• Characterized the SufB2C2 heterotetrameric complex and its cluster-binding properties.
• Performed mutational analyses on *Methanothermococcus thermolithotrophicus* SUF proteins.
• Investigated interactions with methanogenesis marker protein 10 (MmpX).

Main Results:

• The SufB2C2 complex stably binds a [4Fe-4S] cluster, primarily via SufC cysteines.
• SufB enhances ATPase and cluster transfer activities, while SufC is the main cluster binder.
• The complex interacts with MmpX, indicating direct Fe-S cluster transfer.
• Mutations in SufB's conserved residues did not affect cluster binding.

Conclusions:

• The two-protein SUF system in methanogenic archaea is a minimal and potentially ancestral form of Fe-S cluster biogenesis.
• This system operates efficiently without auxiliary proteins, unlike bacterial systems.
• Findings provide insights into early Fe-S cluster assembly and potential applications in synthetic biology.