adenosinetriphosphate binding cassete(ABC) transporter: The human adenosinetriphosphate binding cassete (ABC) have seven subfamilies and 48 members. it ispresent in all the living organisms from human to microorganisms, ABCtransporter can function as influx or efflux.
ABC transporter is a membraneprotein that have the ability to bind and hydrolyze the ATP and use it as a sourceof energy to efflux the substrate out of the cell, this transporter onlyrequire energy to efflux the substance out, in the influx procedure thesubstrate is passively transported to the cell with on need for energy. ABC transportershave an important role in regulating the absorption, distribution, metabolismand execration of cellular lipid and glucose, it controls the glucose and lipidmetabolism by regulate the secretion and activation of insulin and lipase.The structureof ABC transporter:the figurebelow shows the ABC transporter structure which consist of four domains, two ofthem are the binding site, it’s called trance membrane domains, the trancemembrane domains are taking place in the cell membrane, and the other two arethe ATP binding domains which are called nucleotide binding domains, they aretaking place in the cytoplasm, the trance membrane domains binds to thesubstrate and the nucleotide biding domains binds to the ATP molecule. inside cell cytoplasm Outside cell Nucleotide binding domain Trance membrane domain adenosinetriphosphate ride binding cassette B1 (ABCB1):ATP bindingcassette B1 (ABCB1) transporter comes from the ATP binding cassette subfamily Bmember one.it can be classified based on the structure of the polypeptide chainto full and half transporter, if the transporter is composed of one likedpolypeptide chain it’s called full transporter, but if the transporter is presentin tow separated polypeptide chain then it’s called half transporter. Thetransporter uses the energy of ATP hydrolysis to establish a direct membranemovement which create a pocket like structure used to transport the substrateacross the membrane. ABCB1 transporter in the abnormal condition is responsiblefor giving the cancer cells it’s multidrug resisting (MDR1) property, in this casethe transporter can be named as permeability glycoprotein (p-gp).
ABCB1 transporter is present in thebrush porder membrane of the intestinal cells, biliary canalicular membrane ofhepatocyte, luminal membrane of proxima, tubule epithelial cells of the kidney andendothelial cells of blood brain barrier. function ofABCB1:the mainfunction of ATP binding cassette B1 (ABCB1) is to protect the cell by pumpingthe toxic component or metabolite out of the cell by decreasing there exposureto toxic molecules, as a result it limits the entry of the xenobiotic to thecell , it works in decreasing the drug bioavailability by excreting the drugfrom the body by the excretion organs like in the intestine epithelial cellwhere it pumps the drug to the intestinal lumen and in the liver where it pumpsthe drug to the bile duct, and protect the organs by decreasing the exposure ofthe cell to the toxic xenobiotic like in blood brain barrier, testes andplacenta. This transporter Is characterized by its high transporter capacityand its various wide substrate recognition.
When ABCB1 transporter is over excerpted it causesmultidrug resistance(MDR) which is responsible for making the resistance ofdrugs in the cancer cells. permeability glycoprotein (p-gp) is a glycoproteinencoded by the ABCB1 transporter it works in pumping the drugs to outside the cellwhich makes the drug concentration inside the cell much lower than the outside,as a result it protects the cancercell from the anticancer drugs.
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