KŘEČEK, Pavel, SKŮPA, Petr, LIBUS, Jiří, NARAMOTO, S., TEJOS, R., FRIML, J., ZAŽÍMALOVÁ, Eva. The PIN-FORMED (PIN) protein family of auxin transporters. Genome Biology. 2009, 10(12), 249.1-249.11. ISSN 1474-760X. E-ISSN 1474-760X

The PIN-FORMED (PIN) proteins are secondary transporters acting predominantly in the efflux of the plant signal molecule auxin from cells. They are asymmetrically localized within cells and their polarity determines the directionality of intercellular auxin flow. PIN genes are found exclusively in the genomes of multicellular plants and they encode proteins that play an important role in regulating asymmetric auxin distribution in multiple developmental processes. All PIN proteins have similar structure with amino- and carboxy-terminal hydrophobic, membrane-spanning domains separated by a central hydrophilic domain. PIN proteins possessing the large hydrophilic domain localize to plasma membrane. In contrast, those PINs having this domain reduced or lacking localize to endoplasmic reticulum; they regulate subcellular compartmentalization of auxin and thus the auxin metabolism. The activity of PIN proteins is regulated at multiple levels including environmental signals.