Date post: | 18-Dec-2015 |
Category: |
Documents |
Upload: | reynard-chambers |
View: | 214 times |
Download: | 0 times |
ATP Powered Pumps
By Adam Attebery
Introduction
• General information about ATP activated pumps
• Four different classes of ATP activated transmembrane proteins
–Function and examples of each
–Mechanism of each
ATP Powered Pumps
• Transport various small particles against concentration gradient
• All ATP powered pumps are transmembrane with ATP binding site on the cytosolic face of membrane.
4 classes of pumps
• P-class pump– Sodium potassium pumps and calcium pumps
• V-class proton pumps– Plasma membrane of osteoclasts
• F-class proton pumps– Inner mitochondrial membrane
• ABC superfamily– Flippase
P-class Pumps
• All contain two identical catalytic α subunits with ATP binding sites
• In general P-class pumps are ion pumps that move the molecules against concentration gradient
ATP-Powered Ion Pumps
• Ionic composition of the cytosol usually differs greatly from the extracellular fluid
• Cytosolic pH is kept near 7.2 regardless of the extracellular pH
F-class and V-class Pumps
• Structures are similar to one another– Not related to P-class Pumps
• All known F and V-class pumps transport only protons
• V-class pumps maintain low pH at the cost of ATP
• F-class pumps function to power the synthesis of ATP
ABC Superfamily
• Specific to a single substrate or a family of substrates– Ions, sugars, amino acids, phospholipids,
peptides, polysaccharides, or even proteins
• Structural organization consisting of 4 domains– 2 transmembrane domains– 2 cytosolic ATP-binding domains
Summary
• Four classes of transmembrane proteins– Require the hydrolysis of ATP
• Two examples of P-class ATPases– Calcium pump of SR in muscle– Sodium Potassium pump
• Phosphorylation of the alpha subunits and a conformational change are essential for coupling ATP hydrolysis to transport ions
Summary
• V- and F-class ATPases transport protons exclusively– V-class pumps maintain pH– F-class pumps are found in mitochondria and
produce ATP
Summary
• All ABC superfamily proteins contain four core domains– 2 transmembrane domains
• Form pathway for solute movement• Determine substrate specificity
– 2 cytosolic ATP-binding domains
Summary
• ABC superfamily transport a wide array or substrates including:– Toxins– Drugs– Phospholipids– Peptides – Proteins
Summary
• According to the flippase model– Molecules diffuse into cytosolic leaflet
– Flip to exoplasmic leaflet in an ATP powered process
– Finally diffuses from membrane into extracellular space