title: Salt-induced conformational changes in skeletal myosin light chains, troponin-C, and parvalbumin.
abstract: Evidence for salt-induced changes in myosin light chains [dissociated by treatment with 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB)], troponin-C (TnC), and parvalbumin was obtained from chymotryptic digestion, circular dichroism, fluorescence, and difference absorption studies. High salt (0.6 M NaCl) protects the DTNB light chain from proteolysis, increases its alpha-helical content, and quenches the tryptophan fluorescence. These effects are similar to the changes induced by Ca2+ but smaller in magnitude. TnC is affected by monovalent cations in a similar manner. Changes in the alpha-helical content resemble the effect of Ca2+. The enhancement of tyrosine fluorescence reflects conformational changes in the Ca2+-Mg2+ binding sites. The increase in the fluorescence of dansylaziridine-labeled TnC suggests perturbation of Ca2+-specific sites by salt. Cancellation of this effect by Mg2+ binding to the high-affinity sites is indicative of site-site interactions. In Whiting parvalbumin, salt-induced a perturbation of tryptophan absorption similar in nature to the Ca2+ effect.
mesh_terms: D000818:Animals; D002118:Calcium; D002942:Circular Dichroism; D004228:Dithionitrobenzoic Acid; D046911:Macromolecular Substances; D008274:Magnesium; D009124:Muscle Proteins; D009132:Muscles / Q000032:analysis; D009218:Myosins; D009994:Osmolar Concentration; D010320:Parvalbumins; D011487:Protein Conformation; D011817:Rabbits; D012492:Salts; D013050:Spectrometry, Fluorescence; D014336:Troponin
chemical_list: D046911:Macromolecular Substances; D009124:Muscle Proteins; D010320:Parvalbumins; D012492:Salts; D014336:Troponin; D004228:Dithionitrobenzoic Acid; D009218:Myosins; D008274:Magnesium; D002118:Calcium