title: Role of cations in stability of acidic protein Desulfovibrio desulfuricans apoflavodoxin.
abstract: Apoflavodoxin from the sulfate reducing bacteria Desulfovibrio desulfuricans is a small, acidic protein with a net charge of -19 at neutral pH. Here, we show that monovalent cations in biologically relevant amounts have dramatic effects on apoflavodoxin stability. The effect is largest for Gdm(+) and decreases as a function of increased cation charge density (Gdm(+)>NH(4)(+)K(+) approximately Cs(+) approximately Na(+)>Li(+)). A linear correlation of stabilizing effects with cation hydration properties suggests an important role of dehydration in efficient cation interaction with the protein. The effects on stability are due to preferential binding of one cation to native apoflavodoxin and results in an increase in thermal midpoint of 20 degrees C and the free energy of unfolding (at 20 degrees C) increases fivefold. Tuning of biophysical properties (such as folding and ligand/cofactor binding) of acidic proteins by cation binding may be important in vivo.
authors.affiliation: Department of Biochemistry and Cell Biology, Rice University, 6100 Main Street, Houston, TX 77251, USA.
authors.forename: Erik
authors.initials: E
authors.lastname: Sedlák
authors.forename: Loren
authors.initials: L
authors.lastname: Stagg
authors.forename: Pernilla
authors.initials: P
authors.lastname: Wittung-Stafshede
mesh_terms: D001059:Apoproteins / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D002412:Cations; D002942:Circular Dichroism; D045285:Desulfovibrio desulfuricans / Q000737:chemistry*; D019277:Entropy; D005418:Flavodoxin / Q000737:chemistry*; D011489:Protein Denaturation; D013050:Spectrometry, Fluorescence; D055672:Static Electricity
chemical_list: D001059:Apoproteins; D001426:Bacterial Proteins; D002412:Cations; D005418:Flavodoxin; C026932:apoflavodoxin