Molecular Insights into Variable Electron Transfer in Amphibian Cryptochrome

Area of Science:

• Biochemistry
• Molecular Biology
• Photobiology

Background:

• Cryptochrome proteins are blue-light photoreceptors involved in various biological processes.
• Activation involves photoinduced electron transfer, forming radical pairs within the active site.
• Mutagenesis studies suggest alternative electron transfer mechanisms may exist.

Purpose of the Study:

• To computationally investigate alternative electron transfer pathways in Xenopus laevis cryptochrome DASH.
• To elucidate the molecular mechanisms underlying radical pair formation after key amino acid mutations.
• To assess the potential generality of identified pathways across different cryptochrome DASH species.

Main Methods:

• Homology modeling and extensive molecular dynamics (MD) simulations of Xenopus laevis cryptochrome DASH.
• Computational mutagenesis of key amino acid residues involved in electron transfer.
• Tight-binding density-functional theory (TB-DFT) calculations to probe electron transfer pathways.

Main Results:

• Identification of alternative, functionally relevant electron transfer pathways at the molecular level.
• Demonstration that radical pair formation can occur even with mutations in previously identified key residues.
• Sequence comparison suggests one identified pathway may be conserved across cryptochrome DASH proteins.

Conclusions:

• Xenopus laevis cryptochrome DASH possesses alternative electron transfer pathways.
• These pathways offer a potential explanation for observed radical pair formation in mutated cryptochromes.
• A conserved alternative pathway could be a general feature of cryptochrome DASH proteins, impacting their function.