Os01g0121700

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Annotated Information

The name of the gene is half-size adenosine triphosphate-binding cassette transporter subgroup G,OsABCG1or OsWBC1,is a Putative ATP-binding-cassette protein，belongs to the ABC transporter superfamily.

Function

ATP-binding cassette transporters (ABC transporters) are transmembrane proteins that utilize the energy of adenosine triphosphate (ATP) binding and hydrolysis to carry out certain biological processes including translocation of various substrates across membranes and non-transport-related processes such as translation of RNA and DNA repair. They transport a wide variety of substrates across extra- and intracellular membranes, including metabolic products, lipids and sterols, and drugs. Proteins are classified as ABC transporters based on the sequence and organization of their ATP-binding cassette (ABC) domain(s).

ABC proteins are characterized by a highly conserved amino acid region, the ATP binding cassette, also known as the nucleotide binding domain (NBD). This domain contains conserved motifs known as Walker A and Walker B sequences, an ABC signature motif, an H loop, and a Q loop . Half-size ABC proteins consist of only one core unit, while full-size ABC proteins have two or more core units. Full-size ABC proteins can function alone, whereas half-size ABC proteins must form homo- or heterodimers to function as transporters.

Mechanism of function

The general mechanism for the transport cycle of ABC transporters has not been fully elucidated but substantial structural and biochemical data has accumulated to support a model in which ATP binding and hydrolysis is coupled to conformational changes in the transporter. The resting state of all ABC transporters has the NBDs in an open dimer configuration, with low affinity for ATP. This open conformation possesses a chamber accessible to the interior of the transporter. The transport cycle is initiated by binding of substrate to the high-affinity site on the TMDs, which induces conformational changes in the NBDs and enhances the binding of ATP. Two molecules of ATP bind, cooperatively, to form the closed dimer configuration. The closed NBD dimer induces a conformational change in the TMDs such that the TMD opens, forming a chamber with an opening opposite to that of the initial state. The affinity of the substrate to the TMD is reduced, thereby releasing the substrate. Hydrolysis of ATP follows and then sequential release of Pi and then ADP restores the transporter to its basal configuration. Although a common mechanism has been suggested, the order of substrate binding, nucleotide binding and hydrolysis, and conformational changes, as well as interactions between the domains is still debated.

Expression

ATP-binding cassette transporters (ABC transporters) are members of a protein superfamily that is one of the largest and oldest families with representatives in all extant phyla from prokaryotes to humans.

Evolution

Adenosine triphosphate (ATP)-binding cassette (ABC) proteins exist in a wide range of organisms from prokaryotes to eukaryotes.Genome wide analysis of model plants such as Arabidopsis and rice (Oryza sativa L.) has revealed that plants have more than 120 ABC proteins, much more than animals or insects.

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Labs working on this gene

1. Department of Crop Science, Obihiro University of Agricultural and Veterinary Medicine, 2-11 Nishi, Inada, Obihiro, Hokkaido 080-8555, Japan.

References

1. Shuichi Matsuda;Atsushi Funabiki;Kaoru Furukawa;Nozomi Komori;Masanori Koike;Yoshihiko Tokuji;Itsuro Takamure;Kiyoaki Kato Genome-wide analysis and expression profiling of half-size ABC protein subgroup G in rice in response to abiotic stress and phytohormone treatments Molecular Genetics and Genomics, 2012, 287(10): 819-835