RESUMO
Monolayers of charged and neutral phospholipids at the air/water interface containing the cytochromes b5 and c are studied by film balance techniques and by fluorescence microscopy. A new technique is introduced to obtain a defined and homogeneous protein distribution within the membrane. It is shown that both proteins preferentially partition into the fluid membrane phases coexisting with solid lipid domains, thus allowing formation of periodic protein distributions. Protein reconstitution in protein/lipid ratios up to 1:50 does not change the pressure, pi c, corresponding to the main lipid transition but changes the slope in the pressure/area isotherms. It also affects the pressure-induced lipid crystallization, in that the monolayer can be viewed as segregated into a protein-free and a protein-enriched phase. Whereas penetration of cytochrome c into the monolayer is highly dependent on lipid head group charge, this does not hold for cytochrome b. In both cases, monolayer penetration is monotonously reduced with increasing surface pressure, pointing to the dependence of hydrophobic protein-lipid interactions on hydrocarbon chain density.
Assuntos
Grupo dos Citocromos b/metabolismo , Grupo dos Citocromos c/metabolismo , Lipídeos de Membrana/metabolismo , Fosfolipídeos/metabolismo , 1,2-Dipalmitoilfosfatidilcolina/metabolismo , Citocromos b5 , Dimetilaminas/metabolismo , Eletroquímica , Bicamadas Lipídicas/metabolismo , Fluidez de Membrana , Proteínas de Membrana/metabolismo , Microscopia de FluorescênciaRESUMO
Platinum electrodes can be coated with cytochrome b5-phospholipid monolayers by the Langmuir-Blodgett technique. Cyclic voltammetry of a series of dyes shows that the coated electrodes become selective for certain electroactive species. The electron transfer reactions of negatively charged species are inhibited at the modified electrode, whereas positively charged species show enhanced reactivity compared with that at a bare metal electrode.
Assuntos
Grupo dos Citocromos b , Fosfolipídeos , Platina , Animais , Bovinos , Citocromos b5 , Eletroquímica , Eletrodos , OxirreduçãoAssuntos
Bivalves/citologia , Mitocôndrias , Nucleotídeos de Adenina/metabolismo , Animais , Bivalves/metabolismo , Citocromos/metabolismo , Fígado/citologia , Mitocôndrias/metabolismo , Mitocôndrias/ultraestrutura , Moluscos/metabolismo , Músculos/citologia , Consumo de Oxigênio , Pâncreas/citologia , Ratos , Especificidade da EspécieAssuntos
Peixes/metabolismo , Mitocôndrias Hepáticas/metabolismo , Oligoelementos/metabolismo , Animais , Cálcio/metabolismo , Cálcio/farmacologia , Cobre/metabolismo , Cobre/farmacologia , Manganês/metabolismo , Manganês/farmacologia , Mitocôndrias Hepáticas/efeitos dos fármacos , Oligoelementos/farmacologia , Zinco/metabolismo , Zinco/farmacologiaRESUMO
The rate and extent of Cu2+ uptake by rat liver mitochondria was measured under various conditions. 1. The uptake is both greater and faster without an energy supply. 2. The uptake, when occuring in ionic media, has a biphasic character, that is it always slows down after an initial burst, and then re-accelerates. 3. Uptake of Cu2+ in the presence of energy initiates K+ uptake from K+-containing media with accompanying swelling and respiratory stimulation. Depending on the amounts of Cu2+ added and the K+ concentration, an inhibition of respiration later ensues. 4. Chelation of the Cu2+ by substrates (notably glutamate) decreases the effects. 5. Prior exposure to Cu2+ decreases or prevents energy-dependent Ca2+ uptake.
