TABLE 15-2 Comparison of Major Classes of ATP- Powered lon and Small-Molecule Pumps P Class F Class V Class ABC Class Substances Transported H·,Na,K,Ca2+ H only Ions and various small olecule Structural and functional Features Large catalytic cr Multiple transmembrane Multiple transmembran Two transmembrane subunits often two) and cytosolic subunits and cvtosolic subunits become phosphorylated generally function generally use energy for solute; two cytosolic y domains form the pathw: during solute transport; ro synthesize ATP released by ATP hydrolysis ATP-binding domains smaller B sul unIts may on B cytosolic subunit to pump H ions from couple ATP hydrolysis regulate transport ered by movement cytosol to organelle to solute movement of H down an lumens, acidifying them. Domains may be in one eectrochemical gradient or separate subunits Location of Specific Pumps Plasma membrane of Bacterial plasma Vacuolar membranes in Bacterial plasma plants, fungi, bacteria membranes plants, yeast, other fungi membranes famino acid. (H pump sugar, and peptide transporters) Plasma membrane of Inner mitochondrial Endosomal and lysosomal Mammalian endoplasmic higher eukaryotes membrane membrane in animal cells reticulum (transporters (Na/K pump peptides associated with antigen presentation by MHC proteins Apical plasma membrane Thy lakoid membrane of Plasma membrane of of mammalian stomach chloroplast certain acid-secreting animal cells(H/K pump) cells (e.g, osteoclasts some kidney tubule cells Plasma brane of Mammalian plasma all cuk cell membranes(transporters of small molecules lipidlike drugs) Sarcoplasmic reticulum membrane in muscle cells(Ca pump)
☆ The na+-K+ ATPase c-A coupling active transport to ATP hydrolysis. The Na*+pump 3(Na K+- and ouabain- binding site K electrochemical electrochemical gradient gradient Nat-binding CYTOSOL ATP ADP+Pi 2K A P-type pump, coupling active transport to ATP hydrolysis Found in the plasma membrane of virtually all animal cells Functions as an active, energy-driven antiporter Pumps against 10-20 times higher gradient Consumes 1/3 energy requirement in a cell Required to maintain osmotic balance and stabilize cell volume
vThe Na +-K+ ATPase ---A coupling active transport to ATP hydrolysis