| Structural highlights
Function
[RAC1_ORYSJ] Small GTPase playing a general role in disease resistance signaling pathway. Acts downstream of heterotrimeric G protein alpha subunit. Regulates cell death and reactive oxygen species production, probably through NADPH oxidase. Also involved in sphingolipid elicitor (SE)-dependent defense signaling. Activates phytoalexin production and alters defense-related genes. Down-regulates metallothionein 2b, a reactive oxygen scavenger.[1] [2] [3] [4]
Publication Abstract from PubMed
Rac/Rop proteins are Rho-type small GTPases that act as molecular switches in plants. Recent studies have identified these proteins as key components in many major plant signaling pathways, such as innate immunity, pollen tube growth, and root hair formation. In rice, the Rac/Rop protein OsRac1 plays an important role in regulating the production of reactive oxygen species (ROS) by the NADPH oxidase OsRbohB during innate immunity. However, the molecular mechanism by which OsRac1 regulates OsRbohB remains unknown. Here, we report the crystal structure of OsRac1 complexed with the non-hydrolyzable GTP analog guanosine 5'-(beta,gamma-imido)triphosphate at 1.9 A resolution; this represents the first active-form structure of a plant small GTPase. To elucidate the ROS production in rice cells, structural information was used to design OsRac1 mutants that displayed reduced binding to OsRbohB. Only mutations in the OsRac1 Switch I region showed attenuated interactions with OsRbohB in vitro. In particular, Tyr(39) and Asp(45) substitutions suppressed ROS production in rice cells, indicating that these residues are critical for interaction with and activation of OsRbohB. Structural comparison of active-form OsRac1 with AtRop9 in its GDP-bound inactive form showed a large conformational difference in the vicinity of these residues. Our results provide new insights into the molecular mechanism of the immune response through OsRac1 and the various cellular responses associated with plant Rac/Rop proteins.
The Crystal Structure of the Plant Small GTPase OsRac1 Reveals Its Mode of Binding to NADPH Oxidase.,Kosami K, Ohki I, Nagano M, Furuita K, Sugiki T, Kawano Y, Kawasaki T, Fujiwara T, Nakagawa A, Shimamoto K, Kojima C J Biol Chem. 2014 Oct 10;289(41):28569-78. doi: 10.1074/jbc.M114.603282. Epub, 2014 Aug 15. PMID:25128531[5]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ Kawasaki T, Henmi K, Ono E, Hatakeyama S, Iwano M, Satoh H, Shimamoto K. The small GTP-binding protein rac is a regulator of cell death in plants. Proc Natl Acad Sci U S A. 1999 Sep 14;96(19):10922-6. PMID:10485927
- ↑ Ono E, Wong HL, Kawasaki T, Hasegawa M, Kodama O, Shimamoto K. Essential role of the small GTPase Rac in disease resistance of rice. Proc Natl Acad Sci U S A. 2001 Jan 16;98(2):759-64. Epub 2001 Jan 9. PMID:11149940 doi:http://dx.doi.org/10.1073/pnas.021273498
- ↑ Suharsono U, Fujisawa Y, Kawasaki T, Iwasaki Y, Satoh H, Shimamoto K. The heterotrimeric G protein alpha subunit acts upstream of the small GTPase Rac in disease resistance of rice. Proc Natl Acad Sci U S A. 2002 Oct 1;99(20):13307-12. Epub 2002 Sep 17. PMID:12237405 doi:http://dx.doi.org/10.1073/pnas.192244099
- ↑ Wong HL, Sakamoto T, Kawasaki T, Umemura K, Shimamoto K. Down-regulation of metallothionein, a reactive oxygen scavenger, by the small GTPase OsRac1 in rice. Plant Physiol. 2004 Jul;135(3):1447-56. Epub 2004 Jun 25. PMID:15220467 doi:http://dx.doi.org/10.1104/pp.103.036384
- ↑ Kosami K, Ohki I, Nagano M, Furuita K, Sugiki T, Kawano Y, Kawasaki T, Fujiwara T, Nakagawa A, Shimamoto K, Kojima C. The Crystal Structure of the Plant Small GTPase OsRac1 Reveals Its Mode of Binding to NADPH Oxidase. J Biol Chem. 2014 Oct 10;289(41):28569-78. doi: 10.1074/jbc.M114.603282. Epub, 2014 Aug 15. PMID:25128531 doi:http://dx.doi.org/10.1074/jbc.M114.603282
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