Caracterização de uma proteina de 35 KDa isolada de mitocondrias de batata com possivel função termogenica

AUTOR(ES)

Helena Maria Ferreira Leite

DATA DE PUBLICAÇÃO

1993

RESUMO

Early studles from thls laboratory have lndicated that the low degree of coupling between respiration and oxidative phosphorylation in potato mitochondria seems to be related to a 35 KDa protein, present in the inner membrane of those mitochondria, with the ability to translocate H with a: mechanism sensitive to purine nucleotides. In this work, we obtained potato mitochondria with better respiratory control, thanks to modificatlons made in the isolation procedure. In spite of the lsolation method, the respiration rate of these mitochondria ln state IV decreased after additltion of ADP or ATP nucleotides ln the presence of carboxyatractylate (CAT). Binding experiments showed that the mitochondria have the ability to bind 1,3 nmol ATP.mg -1 protein 1,1 nmol ADP. Mg -1 protein; 0,7 nmol GTP. Mg -1proteln. Competition experiments showed the largest affinity of binding of these mltochondria towards adenlne nucleotides. The increase of potato and corn mitochondria membrane potential is dependent on the presence of BSA and purine nucleotides. The presence of BSA and nucleotides dld not affect the membrane potential of red beet roots (Beta vulgaris); bean (Phaseolus vulgaris) and rat liver mltochondria. Antibodies against a 35 KDa protein isolated from potato mitochondria were obtained and, using the Western blotting techique, we verified that the other plant mitochondria in studies in this laboratory, such as corn, red beet roots and bean, have this or a similar protein as shown by cross reactivity wlth these antibodies. In contrast a series of non-plant mitochondria, also studied in thls laboratory, such as those from rat liver, beef heart and T. cruzi epimastigotes did not show cross reactivity with these antibodies. Reconstitution experiments of this protéln and of UCP isolated from brown adipose tissue were performed and showed that, in the system used, they have similar behavior. In the vesicles with protein incorporated, the rate of H+ efflux was larger than in control vesicles, prepared without either protein.

ASSUNTO(S)

mitocondria bioquimica

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