title: Delipidation of cytochrome c oxidase from Rhodobacter sphaeroides destabilizes its quaternary structure.
abstract: Delipidation of detergent-solubilized cytochrome c oxidase isolated from Rhodobacter sphaeroides (Rbs-CcO) has no apparent structural and/or functional effect on the protein, however affects its resistance against thermal or chemical denaturation. Phospholipase A2 (PLA2) hydrolysis of phospholipids that are co-purified with the enzyme removes all but two tightly bound phosphatidylethanolamines. Replacement of the removed phospholipids with nonionic detergent decreases both thermal stability of the enzyme and its resilience against the effect of chemical denaturants such as urea. In contrast to nondelipidated Rbs-CcO, the enzymatic activity of PLA2-treated Rbs-CcO is substantially diminished after exposure to high (>4 M) urea concentration at room temperature without an alteration of its secondary structure. Absorbance spectroscopy and sedimentation velocity experiments revealed a strong correlation between intact tertiary structure of heme regions and quaternary structure, respectively, and the enzymatic activity of the protein. We concluded that phospholipid environment of Rbs-CcO has the protective role for stability of its tertiary and quaternary structures.
authors.affiliation: Department of Biochemistry, The University of Texas Health Science Center, San Antonio, TX 78229-3900, USA; Department of Biophysics, Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 04001 Košice, Slovakia. Electronic address: andrej.musatov@gmail.com.
authors.forename: Andrej
authors.initials: A
authors.lastname: Musatov
authors.affiliation: Department of Biochemistry, The University of Texas Health Science Center, San Antonio, TX 78229-3900, USA; Department of Biochemistry, P.J. Šafárik University, Moyzesova 11, 04001 Košice, Slovakia. Electronic address: rastislav.varhac@upjs.sk.
authors.forename: Rastislav
authors.initials: R
authors.lastname: Varhač
authors.affiliation: Department of Biochemistry, The University of Mississippi Medical Center, Jackson, MS 39216, USA. Electronic address: jhosler@umc.edu.
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Hosler
authors.affiliation: Department of Biochemistry, The University of Texas Health Science Center, San Antonio, TX 78229-3900, USA; Department of Biochemistry, P.J. Šafárik University, Moyzesova 11, 04001 Košice, Slovakia; Centre for Interdisciplinary Biosciences, P.J. Šafárik University, Jesenná 5, 04001 Košice, Slovakia. Electronic address: erik.sedlak@upjs.sk.
authors.forename: Erik
authors.initials: E
authors.lastname: Sedlák
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D003576:Electron Transport Complex IV / Q000737:chemistry*; D008055:Lipids / Q000737:chemistry*; D011489:Protein Denaturation; D020836:Protein Structure, Quaternary; D012242:Rhodobacter sphaeroides / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D008055:Lipids; D003576:Electron Transport Complex IV
keywords: Chemical denaturation; Delipidation; Membrane protein stability; Protein-lipid interaction; Thermal denaturation