BE230_Lecture_5 - Reading for lecture Ch 7 page 254: muscle...

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Reading for lecture Ch 7 page 254: muscle Ca ++ ATPase pump Ch 7 page 256: Na + /K + ATPase pump in plasma membrane Ch 7 page 258-260 ABC proteins + /one glucose symporter Ch 7 page 276: H + /K + ATPase
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Active transport is coupled to ATP hydrolysis Na + /K + -ATPase Sodium potassium pump
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Tetramer α 2 β 2 2 different membrane spanning subunits Large α subunit- transport activity Small β subunit- maturation and assembly of the pump E1 conformation has
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Na / K -ATPase Km binding Na + 0.6mM (<<intracellular [Na + ] of 12mM) Therefore Na + normally fully occupy these sites Affinity of cytosolic K + binding sites is low enough that K + transported inwards dissociate from E1 into cytosol despite the high [K + ]
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During E1 to E2 transition 3 bound Na + become accessible to exoplasmic face, affinity of 3Na + binding sites becomes reduced 3 Na + dissociate one at a time into extracellular medium despite high extracellular [Na + ] Transition to E2 generates 2 high affinity K + sites accessible to exoplasmic face Km for K + binding (0.2mM) << extracellular K + (4mM), sites fill with K + During E2 to E1 transition, 2 bound K + transported inwards, released into cytosol
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How important is Na + /K + ATPase pump? Consumes 33.3% of energy produced by animal cells! 66.6% of energy produced by nerve cells!
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BE230_Lecture_5 - Reading for lecture Ch 7 page 254: muscle...

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