Modulation of function in a minimalist heme-binding membrane protein.

Area of Science:

• Biochemistry
• Protein Engineering
• Membrane Biophysics

Background:

• De novo designed heme-binding proteins mimic natural hemoproteins.
• This study extends de novo design to membrane-soluble proteins using glycophorin A.

Purpose of the Study:

• Investigate the impact of aromatic residues on heme redox potential in a membrane protein model.
• Enhance heme binding affinity and modulate electrochemical properties of artificial membrane hemoproteins.

Main Methods:

• Engineered a functional membrane hemoprotein (ME1) with a bishistidine heme-binding site.
• Introduced a single-point mutation (G25F) to create aromatic interactions with the heme cofactor.
• Measured heme binding affinity and redox potential of the wild-type and mutant proteins.

Main Results:

• The G25F mutation significantly increased binding affinity for iron(III) protoporphyrin IX (10-fold tighter).
• The mutation lowered the redox potential of the heme cofactor to -172 mV.
• Demonstrated successful modulation of cofactor properties in a minimalist membrane hemoprotein.

Conclusions:

• Specific design of aromatic interactions is effective in controlling heme cofactor properties within artificial membrane proteins.
• This approach is vital for developing electron transfer chains in artificial photosynthetic systems.
• Minimalist membrane hemoprotein models offer a platform for precise cofactor property tuning.