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 V-class proton pumps 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