Insights into protein adaptation to a saturated salt environment from the crystal structure of a halophilic 2Fe-2S ferredoxin

Nat Struct Biol. 1996 May;3(5):452-8. doi: 10.1038/nsb0596-452.


Haloarcula marismortui is an archaebacterium that flourishes in the world's saltiest body of water, the Dead Sea. The cytosol of this organism is a supersaturated salt solution in which proteins are soluble and active. The crystal structure of a 2Fe-2S ferredoxin from H. marismortui determined at 1.9 A is similar to those of plant-type 2Fe-2S ferredoxins of known structure, with two important distinctions. The entire surface of the protein is coated with acidic residues except for the vicinity of the iron-sulphur cluster, and there is an insertion of two amphipathic helices near the N-terminus. These form a separate hyperacidic domain whose postulated function to provide extra surface carboxylates for solvation. These data and the fact that bound surface water molecules have on the average 40% more hydrogen bonds than in a typical non-halophilic protein crystal structure support the notion that haloadaptation involves better water binding capacity.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adaptation, Biological*
  • Amino Acid Sequence
  • Amino Acids / analysis
  • Computer Simulation
  • Crystallography, X-Ray
  • Ferredoxins / chemistry*
  • Ferredoxins / classification
  • Halobacteriaceae / chemistry*
  • Models, Molecular
  • Molecular Sequence Data
  • Plants / chemistry
  • Sequence Homology, Amino Acid
  • Surface Properties
  • Water / chemistry


  • 2Fe-2S ferredoxin
  • Amino Acids
  • Ferredoxins
  • Water