Undulating Free Energy Landscapes Buffer Redox Chains from Environmental Fluctuations.

Area of Science:

• Biochemistry
• Photosynthesis research
• Bioenergetics

Background:

• Biological redox chains often feature complex, undulating free energy landscapes.
• The functional advantages of these "roller-coaster" landscapes remain poorly understood.
• Tetraheme proteins are key components in many electron transfer pathways.

Purpose of the Study:

• To investigate the functional benefits of roller-coaster free energy landscapes in biological redox systems.
• To compare the dynamics of native and mutant tetraheme proteins under fluctuating redox conditions.
• To model the impact of fluctuating potentials on cofactor populations.

Main Methods:

• Computational analysis of the tetraheme subunit from *Blastochloris viridis* reaction centers.
• In silico mutation studies to compare wild-type (WT) and hypothetical protein variants.
• Calculation of electron population variations under a time-varying potential simulating redox fluctuations.

Main Results:

• Roller-coaster free energy landscapes effectively buffer redox cofactor populations against environmental potential fluctuations.
• The WT roller-coaster landscape modulates the kinetics of both forward and backward electron transfer.
• This buffering sustains the reduction of critical cofactors, like the photosynthetic chlorophyll special pair.

Conclusions:

• Undulating energy landscapes, despite introducing thermodynamically uphill steps, provide a crucial buffering mechanism in redox chains.
• This buffering is advantageous for maintaining the stability and function of essential biological components, such as those in photosynthesis.
• The study highlights the adaptive significance of complex free energy landscapes in biological electron transfer systems.