title: Is association of labile enediyne chromophore a mutually assured protection for carrier protein?
abstract: Most conjugate proteins undergo both conformational and stability changes on ligand removal. When architecture remains unchanged in the protein holo and apo forms, it is uncertain whether the protein stability also remains unaltered in both of the forms. Neocarzinostatin (NCS), a chromoprotein possessing a potent enediyne chromophore stands for such an instance. Protein-chromophore interaction has not been thoroughly explored previously due to a lack of strategies to independently and simultaneously monitor changes in the NCS conjugates. Here we report a method by which one can detect the signal exclusively from only one of the NCS conjugates without the spectral interference from the other. Stability of the NCS protein is significantly correlated to the protein-bound chromophore, irrespective of denaturation by heat, pH, urea, or ethanol. Despite the similarity in protein backbone conformation, protein stability of the NCS holo form diminishes and equalizes to that of the apo form when the chromophore is released and degraded. Although the enediyne chromophore is highly unstable, it intriguingly protects the protein by which it is protected. Significant mutual reliance between the carrier protein and its naturally associated ligand unveils important information on the NCS drug stability.
authors.affiliation: Department of Chemistry, National Chung Hsing University, Taichung 40227, Taiwan, ROC.
authors.forename: Jayachithra
authors.initials: J
authors.lastname: Kandaswamy
authors.forename: Parameswaran
authors.initials: P
authors.lastname: Hariharan
authors.forename: Thallapuranam Krishnaswamy Suresh
authors.initials: TK
authors.lastname: Kumar
authors.forename: Chin
authors.initials: C
authors.lastname: Yu
authors.forename: Ta-Jung
authors.initials: TJ
authors.lastname: Lu
authors.forename: Der-Hang
authors.initials: DH
authors.lastname: Chin
mesh_terms: D001059:Apoproteins / Q000737:chemistry / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D000431:Ethanol / Q000494:pharmacology; D004996:Ethidium / Q000378:metabolism; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D009682:Magnetic Resonance Spectroscopy; D011487:Protein Conformation; D011489:Protein Denaturation / Q000187:drug effects; D017510:Protein Folding; D015203:Reproducibility of Results; D013816:Thermodynamics; D044366:Transition Temperature / Q000187:drug effects; D014508:Urea / Q000494:pharmacology; D009353:Zinostatin / Q000737:chemistry / Q000378:metabolism*
chemical_list: D001059:Apoproteins; D002352:Carrier Proteins; D000431:Ethanol; D014508:Urea; D009353:Zinostatin; D004996:Ethidium