title: Further characterization of agmatine binding to mitochondrial membranes: involvement of imidazoline I2 receptor.
abstract: Agmatine, a divalent diamine with two positive charges at physiological pH, is transported into the matrix of liver mitochondria by an energy-dependent mechanism, the driving force of which is the electrical membrane potential. Its binding to mitochondrial membranes is studied by applying a thermodynamic treatment of ligand-receptor interactions on the analyses of Scatchard and Hill. The presence of two mono-coordinated binding sites S(1) and S(2), with a negative influence of S(2) on S(1), has been demonstrated. The calculated binding energy is characteristic for weak interactions. S(1) exhibits a lower binding capacity and higher binding affinity both of about two orders of magnitude than S(2). Experiments with idazoxan, a ligand of the mitochondrial imidazoline receptor I(2), demonstrate that S(1) site is localized on this receptor while S(2) is localized on the transport system. S(1) would act as a sensor of exogenous agmatine concentration, thus modulating the transport of the amine by its binding to S(2).
authors.affiliation: Department of Biological Chemistry, University of Padua, Viale G. Colombo 3, 35121, Padua, Italy.
authors.forename: Pamela
authors.initials: P
authors.lastname: Martinis
authors.forename: Valentina
authors.initials: V
authors.lastname: Battaglia
authors.forename: Silvia
authors.initials: S
authors.lastname: Grancara
authors.forename: Lisa
authors.initials: L
authors.lastname: Dalla Via
authors.forename: Vito
authors.initials: V
authors.lastname: Di Noto
authors.forename: Stefania
authors.initials: S
authors.lastname: Saccoccio
authors.forename: Enzo
authors.initials: E
authors.lastname: Agostinelli
authors.forename: Marcantonio
authors.initials: M
authors.lastname: Bragadin
authors.forename: Maria Angelica
authors.initials: MA
authors.lastname: Grillo
authors.forename: Antonio
authors.initials: A
authors.lastname: Toninello
mesh_terms: D000376:Agmatine / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D054755:Imidazoline Receptors / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D013816:Thermodynamics
chemical_list: D054755:Imidazoline Receptors; C487767:imidazoline receptor 2; D000376:Agmatine