title: Ligand binding and conformational states of the photoprotein obelin.
abstract: Many proteins require a non-covalently bound ligand to be functional. How ligand binding affects protein conformation is often unknown. Here we address thermal unfolding of the free and ligand-bound forms of photoprotein obelin. Fluorescence and far-UV circular dichroism (CD) data show that the various ligand-dependent conformational states of obelin differ significantly in stability against thermal unfolding. Binding of coelenterazine and calcium considerably stabilizes obelin. In solution, all obelin structures are similar, except for apo-obelin without calcium. This latter protein is an ensemble of conformational states, the populations of which alter upon increasing temperature.
authors.affiliation: Photobiology Laboratory, Institute of Biophysics, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk 660036, Russia.
authors.forename: Elena V
authors.initials: EV
authors.lastname: Eremeeva
authors.forename: Eugene S
authors.initials: ES
authors.lastname: Vysotski
authors.forename: Adrie H
authors.initials: AH
authors.lastname: Westphal
authors.forename: Carlo P M
authors.initials: CP
authors.lastname: van Mierlo
authors.forename: Willem J H
authors.initials: WJ
authors.lastname: van Berkel
mesh_terms: D002118:Calcium / Q000378:metabolism; D002942:Circular Dichroism; D007093:Imidazoles / Q000378:metabolism; D008164:Luminescent Proteins / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D017510:Protein Folding; D011719:Pyrazines / Q000378:metabolism; D013050:Spectrometry, Fluorescence
chemical_list: D007093:Imidazoles; D008164:Luminescent Proteins; D011719:Pyrazines; C010497:obelin; C017144:coelenterazine; D002118:Calcium