title: Halophilic enzyme activation induced by salts.
abstract: Halophilic archea (halobacteriae) thrive in hypersaline environments, avoiding osmotic shock by increasing the ion concentration of their cytoplasm by up to 3-6 M. To remain folded and active, their constitutive proteins have evolved towards a biased amino acid composition. High salt concentration affects catalytic activity in an enzyme-dependent way and a unified molecular mechanism remains elusive. Here, we have investigated a DNA ligase from Haloferax volcanii (Hv LigN) to show that K(+) triggers catalytic activity by preferentially stabilising a specific conformation in the reaction coordinate. Sodium ions, in turn, do not populate such isoform and the enzyme remains inactive in the presence of this co-solute. Our results show that the halophilic amino acid signature enhances the enzyme's thermodynamic stability, with an indirect effect on its catalytic activity. This model has been successfully applied to reengineer Hv LigN into an enzyme that is catalytically active in the presence of NaCl.
authors.affiliation: Structural Biology Unit, CIC bioGUNE , Bizkaia Technology Park, Building 800, 48160 Derio, Spain.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Ortega
authors.forename: Ana
authors.initials: A
authors.lastname: Laín
authors.forename: Xavier
authors.initials: X
authors.lastname: Tadeo
authors.forename: Blanca
authors.initials: B
authors.lastname: López-Méndez
authors.forename: David
authors.initials: D
authors.lastname: Castaño
authors.forename: Oscar
authors.initials: O
authors.lastname: Millet
mesh_terms: D002384:Catalysis; D011088:DNA Ligases / Q000737:chemistry*; D004789:Enzyme Activation; D019605:Euryarchaeota / Q000201:enzymology*; D011188:Potassium / Q000737:chemistry*; D012492:Salts / Q000737:chemistry*; D012964:Sodium / Q000737:chemistry*
chemical_list: D012492:Salts; D012964:Sodium; D011088:DNA Ligases; D011188:Potassium