Structural insights into temperature-dependent dynamics of METPsc1, a miniaturized electron-transfer protein.

The design of protein-metal complexes is rapidly advancing, with applications spanning catalysis, sensing, and bioremediation. We report a comprehensive investigation of METPsc1, a Miniaturized Electron Transfer Protein, in complex with cadmium. This study elucidates the impact of metal coordination on protein folding and structural dynamics across temperatures from 100 K to 300 K. Our findings reveal that METPsc1, composed of two similar halves stabilized by intramolecular hydrogen bonds, exhibits a unique "clothespin-like" recoil mechanism. This allows it to adapt to metal ions of varying radii, mirroring the flexibility observed in natural rubredoxins. High-resolution crystallography and molecular dynamics simulations unveil concerted backbone motions and subtle temperature-dependent shifts in side-chain conformations, particularly for residues involved in crystal packing. Notably, CdS bond lengths increase with temperature, correlating with anisotropic motions of the sulfur atoms involved in second-shell hydrogen bonding. This suggests a dynamic role of protein matrix upon redox cycling. These insights into METPsc1 highlight its potential for catalysis and contribute to the designing of artificial metalloproteins with functional plasticity.