ATP synthase

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A multimeric protein complex that plays a key role in the energy metabolism of all organisms. The inner membranes of the mitochondria of eukaryotes are covered with these organelles. They appear as particles 8–9 nm in diameter. Each particle has a spherical head piece (the F1 domain) that projects into the matrix of the mitochondrion and contains the catalytic sites for ATP synthesis. Imbedded in the lipid bilayer that forms the inner membrane of the mitochondrion is a cylindrical hydrophobic tailpiece (the Fo domain) that contains a channel for a stream of protons. This powers a rotation generator which is made up of a ring of 10–12 subunits that rotate 50–100 times a second. This rotation force is mechanically coupled to the catalytic sites in the F1 domain. These undergo a cycle of conformational changes which first loosely bind ATP and inorganic phosphate molecules, then rigidly bind the nascent ATP, and finally release it. Together the components of the different domains of ATP synthase contain at least 16 different proteins, and many mutations have been detected in the genes in the nuclei which encode these. Such loss of function mutations are generally lethal when hemizygous or homozygous. There are also two genes located in mtDNA, and individuals with mutations in their mtDNA can survive, provided wild-type mitochondria are also present in their cells. The ATP synthases of bacteria and chloroplasts resemble those of mitochondria with respect to the proteins that occupy the Fo and F1 domains. In bacteria, eight of the genes that encode these proteins are clustered in a single operon. See Chronology, 1973, Boyer; 1981, Walker; adenosine phosphate, chemiosmotic theory, heteroplasmy, Leigh syndrome.

Subjects: Genetics and Genomics.

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