title: Deciphering the molecular structure of cryptolepain in organic solvents.
abstract: Solvent composition plays a major role in stabilizing/destabilizing the forces that are responsible for the native structure of a protein. Often, the solvent composition drives the protein into non-native conformations. Elucidation of such non-native structures provides valuable information about the molecular structure of the protein, which is unavailable otherwise. Inclusion of methanol (non-fluorinated alcohol) or TFE (fluorinated alcohol) in the solvent composition drove cryptolepain, a serine protease and an all-β-protein, into a non-native structure with an enhanced β-sheet or induction of α-helix. These solvents did not much affect cryptolepain under neutral conditions, even at higher concentrations, but the effects were predominant at lower pH, when the protein molecule is under stress. The organic solvent-induced state is partially unfolded with similar characteristics to the molten globule state seen with protein under a variety of conditions. Chemical- or temperature-induced unfolding of cryptolepain in the presence of organic solvent is distinctly different from that in the absence of organic solvent. Such different unfolding provided evidence of two structural variants in the molecular structure of the protein as well as the differential stabilization/destabilization of such structural variants and their sequential unfolding.
authors.affiliation: Molecular Biology Unit, Institute of Medical Sciences, Banaras Hindu University, Varanasi 221005, India.
authors.forename: N K
authors.initials: NK
authors.lastname: Prasanna Kumari
authors.forename: M V
authors.initials: MV
authors.lastname: Jagannadham
mesh_terms: D002942:Circular Dichroism; D031106:Cryptolepis / Q000737:chemistry; D019791:Guanidine / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D000432:Methanol / Q000737:chemistry; D010940:Plant Proteins / Q000737:chemistry* / Q000302:isolation & purification; D011489:Protein Denaturation; D017510:Protein Folding; D055550:Protein Stability; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D057057:Serine Proteases / Q000737:chemistry* / Q000302:isolation & purification; D012996:Solutions; D012997:Solvents / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013696:Temperature; D013816:Thermodynamics
chemical_list: D010940:Plant Proteins; D012996:Solutions; D012997:Solvents; D057057:Serine Proteases; D019791:Guanidine; D000432:Methanol