title: The mechanism of 2,2,2-trichloroacetic acid-induced protein precipitation.
abstract: The mechanism of 2,2,2-trichloroacetic acid (TCA)-induced precipitation of proteins is studied. The TCA-induced protein precipitation curves are observed to be U-shaped. It is bound that the protein-precipitate-inducing effects of TCA are due to the three chloro groups in the molecule. Using cardiotoxin III (CTX III) isolated from the Taiwan cobra (Naja naja atra), as a model protein, we attempt to understand the molecular basis for the TCA-induced effects. Employing circular dichroism, proton-deuterium exchange in conjunction with conventional 2D NMR techniques, and 1-anilino naphthalene-8-sulfonate-binding experiments, we demonstrate that CTX III is in a partially structured state similar to the 'A state' in 3% w/v TCA. It is postulated that the formation of this 'sticky' partial structured 'A state' in the TCA-induced unfolding pathway is responsible for the acid-induced protein precipitation.
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan.
authors.forename: T
authors.initials: T
authors.lastname: Sivaraman
authors.forename: T K
authors.initials: TK
authors.lastname: Kumar
authors.forename: G
authors.initials: G
authors.lastname: Jayaraman
authors.forename: C
authors.initials: C
authors.lastname: Yu
mesh_terms: D011232:Chemical Precipitation; D002942:Circular Dichroism; D004179:Cobra Cardiotoxin Proteins / Q000737:chemistry; D004546:Elapid Venoms / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D009113:Muramidase / Q000737:chemistry / Q000187:drug effects; D011489:Protein Denaturation / Q000187:drug effects; D017510:Protein Folding; D011506:Proteins / Q000737:chemistry* / Q000187:drug effects*; D012710:Serum Albumin, Bovine / Q000737:chemistry / Q000187:drug effects; D014238:Trichloroacetic Acid / Q000494:pharmacology*
chemical_list: D004179:Cobra Cardiotoxin Proteins; D004546:Elapid Venoms; D011506:Proteins; C082202:cardiotoxin III, Naja naja atra; D012710:Serum Albumin, Bovine; D014238:Trichloroacetic Acid; D009113:Muramidase