Lecture 7 - Transport ATPases (Pumps) PDF

Movement against the gradient BIOL2020 Prof. Nicanor González Adenosine triphosphate (ATP) is the source of energy for use and storage at the cellular level. The structure of ATP is a nucleoside triphosphate, consisting of a nitrogenous base (adenine), a ribose sugar, and three serially bonded pho...

Movement against the gradient BIOL2020 Prof. Nicanor González Adenosine triphosphate (ATP) is the source of energy for use and storage at the cellular level. The structure of ATP is a nucleoside triphosphate, consisting of a nitrogenous base (adenine), a ribose sugar, and three serially bonded phosphate groups . ATP → ADP (releases energy) ADP → ATP (requires energy) Movement against the concentration gradient requires ATP Symporters and antiporters Direct active transport involves using ATP to directly pump a solute across a membrane against its electrochemical gradient Symporters and antiporters Indirect active transport involves the transport of a solute in the direction of its increasing electrochemical potential coupled to the facilitated diffusion of a second solute (usually an ion) e.g., Symporters and antiporters Amino acid absorption requires both direct and indirect active transport • Enterocytes • Indirect: Amino acid symporters move amino acids into the enterocytes Direct: ATPase pumps maintain ion gradients The enterocytes want to keep: ● High concentration of H+ in the lumen ● High concentration of Na+ in the lumen ● Low concentration of AAs in the lumen Gut lumen Active transport depends on four types of ATPases P-ATPases Vacuolar-ATPase F-type ATPases ABC-type ATPases Active transport depends on four types of ATPases P-ATPases Vacuolar-ATPase F-type ATPases ABC-type ATPases nucleotide-binding P-ATPases are regulated by phosphorylation adaptor linkers • • • • • • axle phosphorylation proton pump motor There are four types of p-ATPases • P1: transport heavy metals P2: maintain electrochemical gradients P3: membrane potential plants and fungi P4: is a Flippase, moves phospholipids P5: unknown function proton pump inhibitors to prevent excess stomach acidification P2-ATPases that you need to know Sarcoplasmic reticulum or plasma membrane Muscles The Nobel Prize in Chemistry 1997 Jens Skou The Na+/K+ ATPase maintains electrochemical ion gradients in all cells https://pdb101.rcsb.org/motm/118 High Na+ outside High K+ inside • . The Na+/K+ ATPase continually pumps Na+ ions out of the cell and K+ ions into the cell The Na+/K+ ATPase cycles between two conformations • E1 P2 type pumps undergo large conformational changes through the pumping cycle E2 Potassium binding sites of the Na+/K+ ATPase are made of oxygens Potassium Oxygen The two potassium ions (shown here in green) are surrounded on all sides by oxygen atoms from the protein Active transport depends on four types of ATPases P-ATPases Vacuolar-ATPase F-type ATPases ABC-type ATPases Cytoplasm https://pdb101.rcsb.org/motm/219 ATP-driven motor Vacuolar-ATPase linkers ● ● axle ● ● ● ● proton pump motor Lysosome H+ Two rotary motors The ATP-driven motor turns an axle, which turns a second motor (light blue and magenta) that pumps protons across the membrane. The linkers hold the complex together pumps H+ ions to increase acidity in specific organelles (ie., vacuoles, lysosomes) Not phosphorylated V-ATPase is regulated by separating the ATP-powered motor from the proton pumping motor. See the movie and a digested thread https://twitter.com/rubinsteinjohn/status/1458280209501851657 Active transport depends on four types of ATPases P-ATPases Vacuolar-ATPase F-type ATPases ABC-type ATPases F-type ATPases are ATP synthases F stands for “factor” and Fo for oligomycin factor • • ATP synthase moves ions with the concentration gradient to produce ATP In the mitochondrial inner membrane https://pdb101.rcsb.org/motm/72 ATP synthase Like a water mill ● ● ● F0 is an electric motor powered by the flow of H+. F1 motor is a chemical motor, powered by ATP. The two motors are connected together by a stator The F1 motor joins ADP and Pi together by force Phosphate ADP ATP https://www.youtube.com/watch?v=OT5AXGS1aL8&t=1s Active transport depends on four types of ATPases P-ATPases Vacuolar-ATPase F-type ATPases ABC-type ATPases ATP-binding cassette transporters mediate ATP-powered translocation of many substrates across membranes. ● ● ● ● ● ABC transporters have two transmembrane domains (TMDs) that are embedded in the membrane bilayer and two ABCs in the cytoplasm. They contain an ATP-Binding Cassette Two conformational states Heterodimers Importers and exporters Some need a binding protein An ATP-binding cassette is a conserved protein domain ABC domain • Different ABCs All ABC transporters have a shared amino acid sequence in the ABC domain The missing protein in the White mutant fly is an ABC transporter Thomas Hunt Morgan Nobel Prize in Physiology or Medicine in 1933 ABC-type ATPases transport big molecules: metabolites, drugs, amino acids, sugars, peptides and pigment precursors Heterodimerization of ABC ATPases increase the number of solutes • • Brown pigment example: White forms hetero dimers with two other proteins Scarlet and Brown Heterodimers have different solutes Red pigment A relatively small number of ABC transporters move a large number of solutes. How? Summary 4 types of ATPases ● P ● F ● V ● ABC They all use (or make) ATP P2 are important ● Na/K pump ● Ca/H pump ● ATP synthase ABC ATPases transport big molecules V-ATPase and ATP synthase rotate