Characterization of a common intermediate of pea lectin in the folding pathway induced by TFE and HFIP.
When pea lectin was exposed to a low pH range, it was found that the secondary structure of the lectin resisted conformational changes to a large extent up to pH 2.4 and below this pH, a sharp transition was observed which could be due to the presence of 27 acidic amino acid residues present in the protein. The effects of 1,1,1,3,3,3 hexafluoro-isopropanol (HFIP) and 2,2,2-Trifluoroethanol (TFE) on the conformation of pea lectin at pH 2.4 were studied using circular dichroism and fluorescence spectroscopy. Analysis varying the TFE concentration showed that up to 80% TFE (v/v) protein retained the residual beta-structure accompanied by a loss in tertiary structure. A similar conformation is presumed to exist at 4% HFIP (v/v), with an increase in HFIP concentration structural rearrangements occurred and a transition from beta-structure to alpha-helical structure started from 12% HFIP which completed at 30% HFIP. Our studies show the occurrence of a common intermediate in the folding pathway of pea lectin induced by two different fluoroalcohols, which differ in their mode of action to stabilize the secondary structure of a given protein. While TFE was not found to induce any alpha-helical structure, HFIP caused the transition of pea lectin, which is predominantly a beta-sheet protein, to a structure rich in alpha-helical contacts. Thus, our results also point out the possibility of a non-hierarchical model of protein folding in lectins.
Naseem
Farah
F
Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh-202002, India.
Khan
Rizwan Hasan
RH
D002942:Circular Dichroism; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D037121:Plant Lectins / Q000737:chemistry*; D020005:Propanols / Q000494:pharmacology*; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D014270:Trifluoroethanol / Q000494:pharmacology*; D006845:Hydrocarbons, Fluorinated
D037121:Plant Lectins; D020005:Propanols; D014270:Trifluoroethanol; C036292:pea lectin; C001337:hexafluoroisopropanol; D006845:Hydrocarbons, Fluorinated