5ksd
From Proteopedia
Crystal Structure of a Plasma Membrane Proton Pump
Structural highlights
Function[PMA2_ARATH] The plasma membrane H(+) ATPase of plants and fungi generates a proton gradient that drives the active transport of nutrients by H(+)-symport. The resulting external acidification and/or internal alkinization may mediate growth responses. Publication Abstract from PubMedA prerequisite for life is the ability to maintain electrochemical imbalances across biomembranes. In all eukaryotes the plasma membrane potential and secondary transport systems are energized by the activity of P-type ATPase membrane proteins: H+-ATPase (the proton pump) in plants and fungi, and Na+,K+-ATPase (the sodium-potassium pump) in animals. The name P-type derives from the fact that these proteins exploit a phosphorylated reaction cycle intermediate of ATP hydrolysis. The plasma membrane proton pumps belong to the type III P-type ATPase subfamily, whereas Na+,K+-ATPase and Ca2+-ATPase are type II. Electron microscopy has revealed the overall shape of proton pumps, however, an atomic structure has been lacking. Here we present the first structure of a P-type proton pump determined by X-ray crystallography. Ten transmembrane helices and three cytoplasmic domains define the functional unit of ATP-coupled proton transport across the plasma membrane, and the structure is locked in a functional state not previously observed in P-type ATPases. The transmembrane domain reveals a large cavity, which is likely to be filled with water, located near the middle of the membrane plane where it is lined by conserved hydrophilic and charged residues. Proton transport against a high membrane potential is readily explained by this structural arrangement. Crystal structure of the plasma membrane proton pump.,Pedersen BP, Buch-Pedersen MJ, Morth JP, Palmgren MG, Nissen P Nature. 2007 Dec 13;450(7172):1111-4. PMID:18075595[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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