Corrole-protein interactions in H-NOX and HasA.

Area of Science:

• Biochemistry
• Protein Engineering
• Biophysical Chemistry

Background:

• Replacing the native haem cofactor in haem proteins creates novel designer proteins for diverse applications.
• Non-exchangeable ligands in haem analogues can alter cofactor binding compared to native haem.

Purpose of the Study:

• To investigate the binding interactions of a P[double bond, length as m-dash]O corrole cofactor with two functionally distinct hemoproteins: a haem-dependent oxygen sensor (H-NOX) and a haem-scavenging protein (HasA).
• To elucidate how protein-cofactor interactions differ from native haem binding in these hemoproteins.

Main Methods:

• Site-directed mutagenesis to probe critical residues.
• Molecular dynamics simulations to assess protein flexibility and binding.
• Förster resonance energy transfer (FRET) to determine protein conformation and dye-cofactor distances.

Main Results:

• In H-NOX, the P[double bond, length as m-dash]O corrole primarily hydrogen bonds with H102, deviating from native Fe(ii)-O2 stabilization.
• HasA binding involves histidine 83, not the native-interacting H32 or Y75, and results in an extended, apo-like conformation.
• Corrole binding to H-NOX is reduced but still occurs in the absence of H102.

Conclusions:

• Non-natural cofactors can exhibit unexpected binding modes within hemoproteins.
• Protein-cofactor interactions are distinct for P[double bond, length as m-dash]O corrole compared to native haem in H-NOX and HasA.
• Further characterization of these interactions is essential for advancing designer haem protein development.