Mugineic acid, a phytosiderophore

<BODY BGCOLOR="#F0F0F0"> <CENTER> <H1>More VRML Chelates</H1> <H3>by <A HREF="/~barak/">Phillip Barak</A></H3> </CENTER> <HR> <SMALL><I>This noframe version has been provided as a courtesy to those who use a frame-incapable or frame-disabled browser. Frames contribute to the utilization of this site because they permit a text window to reside beside a graphics (VRML) window, offering explanation as to its contents. A properly installed VRML plugin, such as Live3D, CosmoWorld, or WorldView is required for viewing of the 3D graphics component of this page.</SMALL></I> <HR> <P><B>Mugineic acid</B> is an amino acid excreted by some graminaceous (grassy) plants under conditions of iron deficiency as part of a strategy of solubilizing Fe from the root environment for uptake by the plant. Mugineic acid is closely related to its biochemical precursor, nicotinamine, and to a number of other compounds that also have been identified as phytosiderophores in graminaceous plants: 3-hydroxymugineic acid, 2'-deoxymugineic acid, avenic acid, and distichonic acid.</P> <P>The binding coordinating groups are two amine-N, two carboxylate-O, and one <FONT FACE=symbol>a</FONT>-hydroxycarboxylate site (two O), a total of 2 N's and 4 O's, forming a tight octahedron in which the central Fe(III) atom resides.</P> <UL> <LI><A HREF="mugineic.gif">Schematic diagram of mugineic acid (1K)</A></LI> <LI><A HREF="mugineic_ball.wrl">Fe complex of mugineic acid, space-filling model (5K)</A></LI> <LI><A HREF="mugineic_b&s.wrl">Fe complex of mugineic acid, ball and stick model (15K)</A></LI> <LI><A HREF="mugineic_stck.wrl">Fe complex of mugineic acid, stick model (15K)</A></LI> </UL> <P><B><I>CPK Color Key:</I></B> gray, carbon; red, oxygen; blue, nitrogen; purple, iron. Hydrogen atoms have been removed for clarity.</P> <P>The effectiveness of mugineic acid under iron-deficient conditions is dependent not only upon the iron chelating properties of the Fe-mugineic acid complex itself but also upon the presence of a plant membrane carrier that recognizes and absorbs the Fe-mugineic acid complex almost exclusively. </P> <P><SMALL><B>Further reading:</B> <BR>Ma, JF, and K Nomoto. 1996. Effective regulation of iron acquisition in graminaceous plants. The role of mugineic acids as phytosiderophores. <I>Physiol. Plant.</I> 97:609-617.<BR> Mino, Y, et al. 1983. Mugineic acid-iron(III) complex and its structurally analogous cobalt(III) complex: Characterization and implication for absorption and transport of iron in graminaceous plants. <I>J. Am. Chem. Soc.</I> 105:4671-4676. [crystal structure] </SMALL></P> <HR> <P><SMALL><A HREF="/~barak/">Phillip Barak</A> (<A HREF="mailto:pwbarak@facstaff.wisc.edu">pwbarak@facstaff.wisc.edu</A>), <A HREF="">Dept. of Soil Science</A>, University of Wisconsin-Madison. All rights reserved to author. Images and text may not be stored on another server without permission. Last modified (NoFrame version) 28 July 1997.</SMALL></P> </BODY>