title: Phospholipid assisted folding of a denatured heme protein: effect of phosphatidylethanolamine.
abstract: The role of the aminophospholipid, phosphatidylethanolamine (PE), has been well established to act as a non-protein molecular chaperone in the folding and assembly of polytopic membrane proteins. However, such studies with soluble proteins have not been done so far and in particular with the heme proteins. We have used the heme enzyme, horseradish peroxidase (HRP), as the model heme protein and studied the effect of different phospholipids on its refolding from denatured state. Dimyristoylphosphatidylethanolamine (DMPE), a bilayer-forming PE, was able to increase the reactivation yield of denatured HRP upon 30min refolding at 25 degrees C. However, dioleoylphosphatidylethanolamine (DOPE), containing one double bond in the fatty acid chains, which does not favour bilayer organization, did not support proper refolding. The phospholipids with N-methylated head groups, phosphatidylcholines, e.g., DMPC and DOPC showed differential effects when DMPC remained mostly non-supportive while DOPC on the contrary led to inhibition of the refolding of the denatured heme enzyme. Fluorescence spectroscopic studies also indicated changes in the microenvironments of the heme moiety and the single tryptophan residue of HRP in presence of the aminophospholipid.
authors.affiliation: Biophysics Division, Saha Institute of Nuclear Physics, 37 Belgachia Road, 700037, Kolkata, India.
authors.forename: Dilip
authors.initials: D
authors.lastname: Debnath
authors.forename: Shekhar
authors.initials: S
authors.lastname: Bhattacharya
authors.forename: Abhijit
authors.initials: A
authors.lastname: Chakrabarti
mesh_terms: D004134:Dimyristoylphosphatidylcholine / Q000494:pharmacology; D004793:Enzyme Reactivators / Q000494:pharmacology; D006418:Heme / Q000737:chemistry; D006420:Hemeproteins / Q000737:chemistry; D006454:Hemoglobins / Q000737:chemistry; D006735:Horseradish Peroxidase / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D008081:Liposomes; D008956:Models, Chemical; D010713:Phosphatidylcholines / Q000494:pharmacology; D010714:Phosphatidylethanolamines / Q000378:metabolism / Q000494:pharmacology*; D011489:Protein Denaturation; D017510:Protein Folding; D012995:Solubility; D013050:Spectrometry, Fluorescence
chemical_list: C410262:1,2-dioleoyl-glycero-3-phosphatidyl ethanolamine; D004793:Enzyme Reactivators; D006420:Hemeproteins; D006454:Hemoglobins; D008081:Liposomes; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D006418:Heme; D006735:Horseradish Peroxidase; C017251:1,2-oleoylphosphatidylcholine; D004134:Dimyristoylphosphatidylcholine; C018525:1,2-dimyristoylphosphatidylethanolamine