Topography of the subunits of Micrococcus lysodeikticus F1-ATPase |
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Authors: | Alicia Mimbrera Luis Rivas Faustino Mollinedo Emilio Muñoz Vicente Larraga |
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Affiliation: | (1) Instituto de Inmunología y Biología Microbiana, C.S.I.C., Unidad de Biomembranas, Velázquez, 144, Madrid-6, Spain |
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Abstract: | Summary The combined use of proteolytic digestion and lactoperoxidase catalyzed labelling with [125I] applied to membrane-bound or soluble pure F1-ATPase from Micrococcus lysodeikticus has allowed us to establish the topography of its , , and subunits within the protein molecule and with respect to the plane of the membrane.The subunit is most externally located to the membrane bilayer looking towards the cytoplasmic face, a position consistent with its proposed catalytic role. The and subunits lie in an intermediate layer between the subunits and the membrane, in which the subunit occupies a central position within the F1-ATPase molecule in contact with the subunit. The subunit appears to be tightly bound to the F0 component of the ATPase complex, probably buried in the membrane bilayer. A molecular arrangement of M. lysodeikticus ATPase is proposed that, taking into account the subunit stoichiometry 3 3 2 2 (MW 420 000), accommodates the role assigned to each subunit and most, if not all, the known properties of this bacterial energy-transducing protein. |
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