Editing Active transport (section)

== Types of primary active transporters ==

# [[P-type ATPase]]: [[sodium potassium pump]], [[calcium pump]], [[proton pump]]
# [[F-ATPase]]: mitochondrial ATP synthase, chloroplast ATP synthase
# [[V-ATPase]]: vacuolar ATPase
# ABC ([[ATP binding cassette]]) transporter: MDR, [[CFTR]], etc.

Adenosine triphosphate-binding cassette transporters ([[ATP-binding cassette transporter|ABC transporters]]) comprise a large and diverse protein family, often functioning as ATP-driven pumps. Usually, there are several domains involved in the overall transporter protein's structure, including two nucleotide-binding domains that constitute the ATP-binding motif and two hydrophobic transmembrane domains that create the "pore" component. In broad terms, ABC transporters are involved in the import or export of molecules across a cell membrane; yet within the protein family there is an extensive range of function.<ref name=":0">{{Cite journal|last1=Kang|first1=Joohyun|last2=Park|first2=Jiyoung|date=December 6, 2011|title=Plant ABC Transporters|journal= The Arabidopsis Book|volume=9|pages=e0153|doi=10.1199/tab.0153|pmid=22303277|pmc=3268509}}</ref>

In plants, ABC transporters are often found within cell and organelle membranes, such as the mitochondria, chloroplast, and plasma membrane. There is evidence to support that plant ABC transporters play a direct role in pathogen response, phytohormone transport, and detoxification.<ref name=":0" /> Furthermore, certain plant ABC transporters may function in actively exporting volatile compounds<ref name=":1">{{Cite journal|last=Adebesin|first=Funmilayo|date=June 30, 2017|title=Emission of volatile organic compounds from petunia flowers is facilitated by an ABC transporter|journal=Plant Science|volume=356|issue=6345|pages=1386–1388|doi=10.1126/science.aan0826|pmid=28663500|bibcode=2017Sci...356.1386A|s2cid=206658803|doi-access=free|hdl=11245.1/2a6bd9dd-ea94-4c25-95b8-7b16bea44e92|hdl-access=free}}</ref> and antimicrobial metabolites.<ref name=":2">{{Cite journal|last=Crouzet|first=Jerome|date=April 7, 2013|title=NtPDR1, a plasma membrane ABC transporter from Nicotiana tabacum, is involved in diterpene transport|url=https://www.science.org/doi/pdf/10.1126/science.aan0826|journal=Plant Molecular Biology|volume=82|issue=1–2|pages=181–192|via=SpringerLink|doi=10.1007/s11103-013-0053-0|pmid=23564360|s2cid=12276939}}</ref>

In petunia flowers (''Petunia hybrida''), the ABC transporter PhABCG1 is involved in the active transport of volatile organic compounds. PhABCG1 is expressed in the petals of open flowers.  In general, volatile compounds may promote the attraction of seed-dispersal organisms and pollinators, as well as aid in defense, signaling, allelopathy, and protection. To study the protein PhABCG1, transgenic petunia [[RNA interference]] lines were created with decreased ''PhABCG1'' expression levels.  In these transgenic lines, a decrease in emission of volatile compounds was observed. Thus, PhABCG1 is likely involved in the export of volatile compounds. Subsequent experiments involved incubating control and transgenic lines that expressed ''PhABCG1'' to test for transport activity involving different substrates. Ultimately, PhABCG1 is responsible for the protein-mediated transport of volatile organic compounds, such as benzyl alcohol and methylbenzoate, across the plasma membrane.<ref name=":1" />

Additionally in plants, ABC transporters may be involved in the transport of cellular metabolites. Pleiotropic Drug Resistance ABC transporters are hypothesized to be involved in stress response and export antimicrobial metabolites. One example of this type of ABC transporter is the protein NtPDR1. This unique ABC transporter is found in ''Nicotiana tabacum'' BY2 cells and is expressed in the presence of microbial elicitors. NtPDR1 is localized in the root epidermis and aerial trichomes of the plant.  Experiments using antibodies specifically targeting NtPDR1 followed by Western blotting allowed for this determination of localization. Furthermore, it is likely that the protein NtPDR1 actively transports out antimicrobial diterpene molecules, which are toxic to the cell at high levels.<ref name=":2" />