PUMPS (SITES FOR ATPase)
ATP- powered pumps transport ions and various small molecules against the concentration gradients. All ATP powered pumps are transmembrane proteins with one or more binding sites located on the cystolic face of the membrane. These proteins are commonly called ATPases, they normally do not hydrolyse ATP into ADP and Pi unless ions or other molecules are simultaneously transported. The general structure of the four classes of ATP-powered pumps. are shown in Fig-.
The membrane of three classes P, F, and V
transport ions only whereas members of the ABC super family transport small
molecules. All P-class ion pumps posses two identical catalytic alpha subunits
that contains two smaller beta subunits that have regulatory functions.
During the transport process at least one of he alpha subunit is phosphorylated, hence named P-class. This class includes the Na+/K+ ATPase in the plasma membrane which maintains the low cytosolic Na+ and high K+ concentration typical of animal cell.
The H+ pumps that generates and maintains the membrane electric potential in the plants, fungal and the bacterial cells also belongs to this class. The structure of the F-class and V-class are similar to one another and more complicated than P-class pump. F and V class contains several different transmembrane and cystolic subunits.
V-class pumps generally function to maintain the low pH of the plant vacuoles and of the lysosomes by pumping protons from the cytosolic to the exoplasmic face of the membrane against a protin electrochemical gradient.
F-class pumps are found in the bacterial plasma membrane and in the chloroplast and mitochondria. In contrast to V- class pumps,
F-class pump generally function to power the synthesis of ATP from ADP and Pi by the movement of proton from the exoplasmic to the cytosolic face of the membrane down the electrochemical gradient.
The ABC super family includes several hundred different transport proteins. Each ABC protein is specific for a single substrate or group of related substrate, which may be ions, amino acid, sugars, phospholipids, peptides, polysaccharides, or even proteins. All ABC trasport proteins shares. A structural organization consisting of four “core” domains: two transmembrane domains forming the passageway through which transported molecules cross the membrane and the two cytosolic ATP binding domains. In some ABC proteins mostly in the bacteria the core domains are present in four separate polypeptides
ATP- powered pumps transport ions and various small molecules against the concentration gradients. All ATP powered pumps are transmembrane proteins with one or more binding sites located on the cystolic face of the membrane. These proteins are commonly called ATPases, they normally do not hydrolyse ATP into ADP and Pi unless ions or other molecules are simultaneously transported. The general structure of the four classes of ATP-powered pumps. are shown in Fig-.
During the transport process at least one of he alpha subunit is phosphorylated, hence named P-class. This class includes the Na+/K+ ATPase in the plasma membrane which maintains the low cytosolic Na+ and high K+ concentration typical of animal cell.
The H+ pumps that generates and maintains the membrane electric potential in the plants, fungal and the bacterial cells also belongs to this class. The structure of the F-class and V-class are similar to one another and more complicated than P-class pump. F and V class contains several different transmembrane and cystolic subunits.
V-class pumps generally function to maintain the low pH of the plant vacuoles and of the lysosomes by pumping protons from the cytosolic to the exoplasmic face of the membrane against a protin electrochemical gradient.
F-class pumps are found in the bacterial plasma membrane and in the chloroplast and mitochondria. In contrast to V- class pumps,
F-class pump generally function to power the synthesis of ATP from ADP and Pi by the movement of proton from the exoplasmic to the cytosolic face of the membrane down the electrochemical gradient.
The ABC super family includes several hundred different transport proteins. Each ABC protein is specific for a single substrate or group of related substrate, which may be ions, amino acid, sugars, phospholipids, peptides, polysaccharides, or even proteins. All ABC trasport proteins shares. A structural organization consisting of four “core” domains: two transmembrane domains forming the passageway through which transported molecules cross the membrane and the two cytosolic ATP binding domains. In some ABC proteins mostly in the bacteria the core domains are present in four separate polypeptides
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