title: Lipid unsaturation per se does not explain the physical state of mitochondrial membranes in Mytilus galloprovincialis.
abstract: Through a multiple approach, the present study on the mitochondrial membranes from mussel gills and swine heart combines some biochemical information on fatty acid composition, sterol pattern, and temperature dependence of the F1FO-ATPase activity (EC 3.6.3.14.) with fluorescence data on mitochondrial membranes and on liposomes obtained from lipid extracts of mitochondria. The physical state of mussel gills and swine heart was investigated by Laurdan steady state fluorescence. Quite surprisingly, the similar temperature dependence of the F1FO complex, illustrated as Arrhenius plot which in both mitochondria exhibits the same discontinuity at approximately 21°C and overlapping activation energies above and below the discontinuity, is apparently compatible with a different composition and physical state of mitochondrial membranes. Accordingly, mussel membranes contain highly unsaturated fatty acids, abundant sterols, including phytosterols, while mammalian membranes only contain cholesterol and in prevalence shorter and less unsaturated fatty acids, leading to a lower membrane unsaturation with respect to mussel mitochondria. As suggested by fluorescence data, the likely formation of peculiar microdomains interacting with the membrane-bound enzyme complex in mussel mitochondria could produce an environment which somehow approaches the physical state of mammalian mitochondrial membranes. Thus, as an adaptive strategy, the interaction between sterols, highly unsaturated phospholipids and proteins in mussel gill mitochondria could allow the F1FO-ATPase activity to maintain the same activation energy as the mammalian enzyme.
authors.affiliation: Department of Life and Environmental Sciences, Marche Polytechnic University, Montedago, 60131 Ancona, Italy. Electronic address: r.fiorini@univpm.it.
authors.forename: Rosamaria
authors.initials: R
authors.lastname: Fiorini
authors.affiliation: Department of Veterinary Medical Sciences, University of Bologna, 40064 Ozzano Emilia, Bologna, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Pagliarani
authors.affiliation: Department of Veterinary Medical Sciences, University of Bologna, 40064 Ozzano Emilia, Bologna, Italy.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Nesci
authors.affiliation: Department of Veterinary Medical Sciences, University of Bologna, 40064 Ozzano Emilia, Bologna, Italy.
authors.forename: Fabiana
authors.initials: F
authors.lastname: Trombetti
authors.affiliation: Department of Veterinary Medical Sciences, University of Bologna, 40064 Ozzano Emilia, Bologna, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Pirini
authors.affiliation: Department of Veterinary Medical Sciences, University of Bologna, 40064 Ozzano Emilia, Bologna, Italy.
authors.forename: Micaela
authors.initials: M
authors.lastname: Fabbri
authors.affiliation: Department of Veterinary Medical Sciences, University of Bologna, 40064 Ozzano Emilia, Bologna, Italy.
authors.forename: Vittoria
authors.initials: V
authors.lastname: Ventrella
mesh_terms: D000818:Animals; D005227:Fatty Acids / Q000737:chemistry* / Q000378:metabolism*; D005880:Gills / Q000166:cytology; D051336:Mitochondrial Membranes / Q000378:metabolism*; D049878:Mytilus / Q000166:cytology*; D006180:Proton-Translocating ATPases / Q000378:metabolism; D013261:Sterols / Q000378:metabolism*; D013552:Swine; D013696:Temperature
chemical_list: D005227:Fatty Acids; D013261:Sterols; D006180:Proton-Translocating ATPases
keywords: F(1)F(O)–ATPase; Fatty acids; Laurdan; Mitochondrial membranes; Mussel