Structure and Function of a Bacterial Microcompartment Shell Protein Engineered to Bind a [4Fe-4S] Cluster.

Area of Science:

• Biochemistry
• Structural Biology
• Biotechnology

Background:

• Bacterial microcompartments (BMCs) are protein-based organelles with permeable shells, useful for bionanoreactors.
• Electron transfer across BMC shells is crucial for encapsulating oxidoreductive reactions.

Purpose of the Study:

• To engineer a BMC shell protein capable of electron transfer for bionanoreactor applications.
• To create a functional [4Fe-4S] cluster-binding site within a BMC shell protein.

Main Methods:

• Determined crystal structure of a BMC shell protein component.
• Designed and incorporated a [4Fe-4S] cluster-binding site.
• Solved the structure of the engineered protein containing the metal center.
• Characterized the [4Fe-4S] cluster using optical and EPR spectroscopies.

Main Results:

• The engineered BMC shell protein successfully binds a [4Fe-4S] cluster.
• The structure of the engineered protein with the metal center was solved to 1.8 Å resolution.
• The [4Fe-4S] cluster exhibits a low reduction potential (-370 mV vs SHE) and stability through redox cycling.
• The cluster's stability is attributed to the protein scaffold's hydrogen-bonding network.

Conclusions:

• The engineered BMC shell protein provides a foundation for electron-transfer functionality.
• This work paves the way for developing advanced bionanoreactors with tunable electron transfer properties.
• The findings offer insights into metal center ligation within protein scaffolds.