|PROSITE documentation PDOC51142|
Iron is essential for fundamental cellular processes such as electron transfer in photosynthesis, respiration, nitrogen fixation as well as DNA synthesis. Ferric iron has an extremely low solubility and is not readily available to plants in the soils. To mobilize iron, plants have evolved at least two sophisticated and tightly regulated mechanisms for the acquisition of iron from soil. Strategy I plants, including dicots and nongraminaceous monocots, facilitate iron uptake mainly by increased acidification of the rhizosphere due to enhanced proton extrusion and the reduction of Fe(III) to Fe(II) by an inducible plasma membrane-bound reductase. In contrast, graminaceous monocots (strategy II plants) release phytosiderophores of the mugineic acid family into the rhizosphere. These compounds act as chelator of ferric ions and are taken up by root cells as Fe(III)-phytosiderophore complexes [1,2,3,4].
The nonproteinogenous amino acid nicotianamine (NA) is found in all multicellular plants and is considered to be a key component for both strategies of iron acquisition of all plants. In graminaceous plants, it is the first intermediate in the synthesis of the phytosiderophores of the mugineic acid type. In nongraminaceous plants, NA is necessary for Fe homeostasis and has been implicated in the internal transport of metal ions. Nicotianamine synthase (NAS) (EC 188.8.131.52) catalyzes the complicated reaction in which three S-adenosylmethionine (SAM) molecules are conjugated into one NA molecule in a single step [1,2,3,4].
The profile we developed covers the entire NAS protein.Last update:
August 2005 / First entry.
PROSITE method (with tools and information) covered by this documentation:
|1||Authors||Higuchi K. Suzuki K. Nakanishi H. Yamaguchi H. Nishizawa N.-K. Mori S.|
|Title||Cloning of nicotianamine synthase genes, novel genes involved in the biosynthesis of phytosiderophores.|
|Source||Plant Physiol. 119:471-480(1999).|
|2||Authors||Ling H.-Q. Koch G. Baeumlein H. Ganal M.W.|
|Title||Map-based cloning of chloronerva, a gene involved in iron uptake of higher plants encoding nicotianamine synthase.|
|Source||Proc. Natl. Acad. Sci. U.S.A. 96:7098-7103(1999).|
|3||Authors||Herbik A. Koch G. Mock H.-P. Dushkov D. Czihal A. Thielmann J. Stephan U.W. Baeumlein H.|
|Title||Isolation, characterization and cDNA cloning of nicotianamine synthase from barley. A key enzyme for iron homeostasis in plants.|
|Source||Eur. J. Biochem. 265:231-239(1999).|
|4||Authors||Mizuno D. Higuchi K. Sakamoto T. Nakanishi H. Mori S. Nishizawa N.K.|
|Title||Three nicotianamine synthase genes isolated from maize are differentially regulated by iron nutritional status.|
|Source||Plant Physiol. 132:1989-1997(2003).|