{PDOC51142}
{PS51142; NAS}
{BEGIN}
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* Nicotianamine synthase (NAS)-like family profile *
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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 [1-4].

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 2.5.1.43) catalyzes the complicated reaction
in which three S-adenosylmethionine (SAM) molecules are conjugated into one NA
molecule in a single step [1-4].

NAS-like proteins are also found in fungi and in methanogenic archaea [2,3].

The profile we developed covers the entire NAS protein.

-Sequences known to belong to this class detected by the profile: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.
-Last update: August 2005 / First entry.

[ 1] Higuchi K., Suzuki K., Nakanishi H., Yamaguchi H., Nishizawa N.-K.,
     Mori S.
     "Cloning of nicotianamine synthase genes, novel genes involved in the
     biosynthesis of phytosiderophores."
     Plant Physiol. 119:471-480(1999).
     PubMed=9952442
[ 2] Ling H.-Q., Koch G., Baeumlein H., Ganal M.W.
     "Map-based cloning of chloronerva, a gene involved in iron uptake of
     higher plants encoding nicotianamine synthase."
     Proc. Natl. Acad. Sci. U.S.A. 96:7098-7103(1999).
     PubMed=10359845
[ 3] Herbik A., Koch G., Mock H.-P., Dushkov D., Czihal A., Thielmann J.,
     Stephan U.W., Baeumlein H.
     "Isolation, characterization and cDNA cloning of nicotianamine
     synthase from barley. A key enzyme for iron homeostasis in plants."
     Eur. J. Biochem. 265:231-239(1999).
     PubMed=10491178
[ 4] Mizuno D., Higuchi K., Sakamoto T., Nakanishi H., Mori S.,
     Nishizawa N.K.
     "Three nicotianamine synthase genes isolated from maize are
     differentially regulated by iron nutritional status."
     Plant Physiol. 132:1989-1997(2003).
     PubMed=12913155

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