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15.10, 589 ATP-dependent ion pumps—maintain ion gradients against concentration gradient -20-50% of all ATP hydrolyzed used by these pumps-even in muscle -if you poison ATP synthesis, eventually ions will come to equilibrium across membrane (all cells have a certain rate of leakage of ions across membrane)-constantly bailing the boat -many think that ion pumps are responsible for metabolic rate 15-2, 590 15.11, 592 Calcium ATPase, sometimes called SERCA -what moves calcium in your muscle-allows muscle to contract and relax ~1000 amino acids, and over 200 have been studied by sitedirected mutagenesis MacLennan, DH and Toyofuku, T. 1996. Regulatory interactions between calcium atpases and phospholamban. Organellar Ion Channels and Transporters. Rockefeller Univ. Press. -isoforms for slow muscle, fast, smooth, nonmuscle (plasma membrane) -switch muscle type switch SERCA also I found that marlin make a juvenile form of SERCA in their heater tissue. Does this contribute to heat production, or do all vertebrates have SERCA 1B in their eye muscles (just because eye muscles are weird)? 1 2 3 4 5 300 bp Tyson Cramer showed that rats make 1A (adult version)but chickens make 1B; so not all verts have 1B in eye muscle. 15-13, 593 Na+/K+ ATPase-another well-studied pump BLOCKED BY OABAIN Km=.2 mM vs. 4 mM outside (K+) Km=.6 mM vs. 12 mM inside (Na+) p. 648 V-type pumps move protons against their concentration gradient-used to acidify vesicles (lysosome, CURL) ATP ~5 ADP ~7 Acid-secreting cells, like this one from toad bladder-almost solid with V-type pumps 15-14, 594 100 X differencecan't pump H+ forever-would build up huge charge gradient which would oppose any further movement of H+ -either 1 cation out for 1 cation in or cation in, anion out 15-16, 596 MDR, or multi-drug resistance transport protein -ATP hydrolysis used to export small hydrophobic molecules -activity correlated with exposure to toxins-often thwarts efforts of chemotherapy-can be used as an indicator of exposure to pollution -CFTR protein, a chloride channel that is defected in cystic fibrosis patients, is similar in structure to MDR Group Exercise # 11 Come up with an analogy that explains how a Na+/K+ pump works. Imagine you are explaining this to a 4th grade class.