ABCB

ABCB refers to the ATP-binding cassette sub-family B, a group within the larger ATP-binding cassette (ABC) transporter superfamily. Members of this subfamily are membrane proteins that harness energy from ATP hydrolysis to move diverse substrates across cellular membranes. In eukaryotes, ABCB transporters typically feature two nucleotide-binding domains and two transmembrane domains, forming full-size transporters anchored in membranes such as the plasma membrane, endoplasmic reticulum, or canalicular membranes of liver cells. They play roles in xenobiotic efflux, lipid transport, antigen processing, and homeostasis of heme and metals, among other processes.

Several human ABCB transporters are well studied. ABCB1, also known as P-glycoprotein or MDR1, is a broad-spectrum efflux pump that expels drugs and toxins from cells and is a key contributor to multidrug resistance in cancer. ABCB4 (MDR3) is a phospholipid transporter in the canalicular membrane of hepatocytes; mutations can cause cholestasis and progressive liver disease. ABCB11 (BSEP) exports bile salts into bile and is essential for bile formation; defects can lead to cholestatic disorders. The TAP proteins, ABCB2 (TAP1) and ABCB3 (TAP2), form a heterodimer that transports antigenic peptides into the endoplasmic reticulum for MHC class I presentation. ABCB5 and other members have roles in skin biology and cancer, while mitochondrial-localized transporters such as ABCB6 and ABCB7 participate in porphyrin transport and iron-sulfur cluster export, respectively.

ABCB transporters are conserved across many species and show tissue-specific expression patterns. Their diverse functions influence pharmacokinetics, immune surveillance, liver physiology, and cellular metabolism. Given their roles in drug disposition and disease, they remain important targets in pharmacology and medical genetics.