Structural insights from water-ferredoxin interaction in mesophilic algae and halophilic archaea.

We analyzed the water-ferredoxin interaction in mesophilic (moderate temperature) algae (PDB ID: 1AWD) and halophilic (salt-tolerant) archaea (PDB ID: 1DOI) using POWAIND version 2.0 (a protein-water interactions calculation program). It is found that the shell water (SW) is 2.5 fold greater in halophilic ferredoxin than mesophilic ferredoxin. Water-ferredoxin interactions in the core and cavity are the signature of stability. The normalized frequency of such interactions is less in halophilic relative to mesophilic ferredoxin and the halophilic signature for stability by such interactions is negligible. However, the surface dominated with such interactions seems to be important for ferredoxin and oxido-reductase recognition.