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Multi-Drug Resistance

Mechanisms in Multi-drug Resistance: ABC-transporters and detoxification enzymes in hepatocytes
The cellular components responsible for the phenomenon of Multi-drug Resistance (MDR) in the structural context of hepatocytes include intrinsic transmembrane proteins, generically called drug efflux pumps and the enzymes responsible for detoxification and biotransformation of xenobiotics.
The enzymes include the cytochrome P450 (CYPs) and the Phase II conjugation enzymes such as Glutathione-S-Transferase (GST). The major drug efflux pumps are in the superfamily of ABC (ATP-Binding-Cassette)-Transporters. Of these ABC-ATPases, the major subfamilies are the MDR/TAPs and MRPs (multidrug resistance related proteins). The natural substrates are also shown for the drug efflux pumps illustrated.