AUTHOR=Talon Romain , Coquelle Nicolas , Madern Dominique , Girard Eric 

TITLE=An experimental point of view on hydration/solvation in halophilic proteins

JOURNAL=Frontiers in Microbiology

VOLUME=5

YEAR=2014

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2014.00066

DOI=10.3389/fmicb.2014.00066

ISSN=1664-302X

ABSTRACT=<p>Protein-solvent interactions govern the behaviors of proteins isolated from extreme halophiles. In this work, we compared the solvent envelopes of two orthologous tetrameric malate dehydrogenases (MalDHs) from halophilic and non-halophilic bacteria. The crystal structure of the MalDH from the non-halophilic bacterium <italic>Chloroflexus aurantiacus</italic> (<italic>Ca</italic> MalDH) solved, <italic>de novo</italic>, at 1.7 Å resolution exhibits numerous water molecules in its solvation shell. We observed that a large number of these water molecules are arranged in pentagonal polygons in the first hydration shell of <italic>Ca</italic> MalDH. Some of them are clustered in large networks, which cover non-polar amino acid surface. The crystal structure of MalDH from the extreme halophilic bacterium <italic>Salinibacter ruber</italic> (<italic>Sr</italic>) solved at 1.55 Å resolution shows that its surface is strongly enriched in acidic amino acids. The structural comparison of these two models is the first direct observation of the relative impact of acidic surface enrichment on the water structure organization between a halophilic protein and its non-adapted counterpart. The data show that surface acidic amino acids disrupt pentagonal water networks in the hydration shell. These crystallographic observations are discussed with respect to halophilic protein behaviors in solution</p>