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See detailSubunit Asa1 spans all the peripheral stalk of the mitochondrial ATP synthase of the chlorophycean alga Polytomella sp.
Colina-Tenorio, Lilia; Miranda-Astudillo, Hector; Cano-Estrada, Araceli et al

in Biochimica et biophysica acta (2016)

Mitochondrial F1FO-ATP synthase of chlorophycean algae is dimeric. It contains eight orthodox subunits (alpha, beta, gamma, delta, epsilon, OSCP, a and c) and nine atypical subunits (Asa1 to 9). These ... [more ▼]

Mitochondrial F1FO-ATP synthase of chlorophycean algae is dimeric. It contains eight orthodox subunits (alpha, beta, gamma, delta, epsilon, OSCP, a and c) and nine atypical subunits (Asa1 to 9). These subunits build the peripheral stalk of the enzyme and stabilize its dimeric structure. The location of the 66.1kDa subunit Asa1 has been debated. On one hand, it was found in a transient subcomplex that contained membrane-bound subunits Asa1/Asa3/Asa5/Asa8/a (Atp6)/c (Atp9). On the other hand, Asa1 was proposed to form the bulky structure of the peripheral stalk that contacts the OSCP subunit in the F1 sector. Here, we overexpressed and purified the recombinant proteins Asa1 and OSCP and explored their interactions in vitro, using immunochemical techniques and affinity chromatography. Asa1 and OSCP interact strongly, and the carboxy-terminal half of OSCP seems to be instrumental for this association. In addition, the algal ATP synthase was partially dissociated at relatively high detergent concentrations, and an Asa1/Asa3/Asa5/Asa8/a/c10 subcomplex was identified. Furthermore, Far-Western analysis suggests an Asa1-Asa8 interaction. Based on these results, a model is proposed in which Asa1 spans the whole peripheral arm of the enzyme, from a region close to the matrix-exposed side of the mitochondrial inner membrane to the F1 region where OSCP is located. 3D models show elongated, helix-rich structures for chlorophycean Asa1 subunits. Asa1 subunit probably plays a scaffolding role in the peripheral stalk analogous to the one of subunit b in orthodox mitochondrial enzymes. [less ▲]

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See detailInteractions of subunits Asa2, Asa4 and Asa7 in the peripheral stalk of the mitochondrial ATP synthase of the chlorophycean alga Polytomella sp.
Miranda-Astudillo, Hector; Cano-Estrada, Araceli; Vazquez-Acevedo, Miriam et al

in Biochimica et Biophysica Acta-Bioenergetics (2014), 1837

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See detail3D-reconstruction and overall topology of the dimeric mitochondrial ATP synthase of the colorless alga Polytomella sp
González-Halphen, Diego; Vázquez-Acevedo, Myriam; Cano-Estrada, Araceli et al

in Biochimica et Biophysica Acta (BBA) - Bioenergetics (2010, July), 1797(Supplement 1), 32

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See detailThe fully-active and structurally-stable form of the mitochondrial ATP synthase of Polytomella sp is dimeric
Villavicencio-Queijeiro, Alexa; Vazquez-Acevedo, Miriam; Cano-Estrada, Araceli et al

in Journal of Bioenergetics & Biomembranes (2009), 41(1), 1-13

Mitochondrial F1FO-ATP synthase of chlorophycean algae is a stable dimeric complex of 1,600 kDa. It lacks the classic subunits that constitute the peripheral stator-stalk and the orthodox polypeptides ... [more ▼]

Mitochondrial F1FO-ATP synthase of chlorophycean algae is a stable dimeric complex of 1,600 kDa. It lacks the classic subunits that constitute the peripheral stator-stalk and the orthodox polypeptides involved in the dimerization of the complex. Instead, it contains nine polypeptides of unknown evolutionary origin named ASA1 to ASA9. The isolated enzyme exhibited a very low ATPase activity (0.03 Units/mg), that increased upon heat treatment, due to the release of the F-1 sector. Oligomycin was found to stabilize the dimeric structure of the enzyme, providing partial resistance to heat dissociation. Incubation in the presence of low concentrations of several non-ionic detergents increased the oligomycin-sensitive ATPase activity up to 7.0-9.0 Units/mg. Incubation with 3% (w/v) taurodeoxycholate monomerized the enzyme. The monomeric form of the enzyme exhibited diminished activity in the presence of detergents and diminished oligomycin sensitivity. Cross-linking experiments carried out with the dimeric and monomeric forms of the ATP synthase suggested the participation of the ASA6 subunit in the dimerization of the enzyme. The dimeric enzyme was more resistant to heat treatment, high hydrostatic pressures, and protease digestion than the monomeric enzyme, which was readily disrupted by these treatments. We conclude that the fully-active algal mitochondrial ATP synthase is a stable catalytically active dimer; the monomeric form is less active and less stable. Monomer-monomer interactions could be mediated by the membrane-bound subunits ASA6 and ASA9, and may be further stabilized by other polypeptides such as ASA1 and ASA5. [less ▲]

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See detailThe mitochondrial ATP synthase of chlorophycean algae contains eight subunits of unknown origin involved in the formation of an atypical stator-stalk and in the dimerization of the complex
Vazquez-Acevedo, Miriam; Cardol, Pierre ULg; Cano-Estrada, Araceli et al

in Journal of Bioenergetics & Biomembranes (2006), 38(5-6), 271-282

Mitochondrial F1FO-ATP synthase of Chlamydomonas reinhardtii and Polytomella sp. is a dimer of 1,600,000 Da. In Chlamydomonas the enzyme lacks the classical subunits that constitute the peripheral stator ... [more ▼]

Mitochondrial F1FO-ATP synthase of Chlamydomonas reinhardtii and Polytomella sp. is a dimer of 1,600,000 Da. In Chlamydomonas the enzyme lacks the classical subunits that constitute the peripheral stator-stalk as well as those involved in the dimerization of the fungal and mammal complex. Instead, it contains eight novel polypeptides named ASA1 to 8. We show that homologs of these subunits are also present in the chlorophycean algae Polytomella sp. and Volvox carterii. Blue Native Gel Electrophoresis analysis of mitochondria from different green algal species also indicates that stable dimeric mitochondrial ATP synthases may be characteristic of all Chlorophyceae. One additional subunit, ASA9, was identified in the purified mitochondrial ATP synthase of Polytomella sp. The dissociation profile of the Polytomella enzyme at high-temperatures and cross-linking experiments finally suggest that some of the ASA polypeptides constitute a stator-stalk with a unique architecture, while others may be involved in the formation of a highly-stable dimeric complex. The algal enzyme seems to have modified the structural features of its surrounding scaffold, while conserving almost intact the structure of its catalytic subunits. [less ▲]

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