View source for 1afb

[[Image:1afb.gif|left|200px]]<br /><applet load="1afb" size="450" color="white" frame="true" align="right" spinBox="true" 
caption="1afb, resolution 1.9&Aring;" />
'''STRUCTURAL BASIS OF GALACTOSE RECOGNITION IN C-TYPE ANIMAL LECTINS'''<br />

==Overview==
The asialoglycoprotein receptors and many other C-type (Ca2+-dependent), animal lectins specifically recognize galactose- or, N-acetylgalactosamine-terminated oligosaccharides. Analogous binding, specificity can be engineered into the homologous rat mannose-binding, protein A by changing three amino acids and inserting a glycine-rich loop, (Iobst, S. T., and Drickamer, K. (1994) J. Biol. Chem. 269, 15512-15519)., Crystal structures of this mutant complexed with beta-methyl galactoside, and N-acetylgalactosamine (GalNAc) reveal that as with wild-type, mannose-binding proteins, the 3- and 4-OH groups of the sugar directly, coordinate Ca2+ and form hydrogen bonds with amino acids that also serve, as Ca2+ ligands. The different stereochemistry of the 3- and 4-OH groups, in mannose and galactose, combined with a fixed Ca2+ coordination, geometry, leads to different pyranose ring locations in the two cases. The, glycine-rich loop provides selectivity against mannose by holding a, critical tryptophan in a position optimal for packing with the apolar face, of galactose but incompatible with mannose binding. The 2-acetamido, substituent of GalNAc is in the vicinity of amino acid positions, identified by site-directed mutagenesis (Iobst, S. T., and Drickamer, K., (1996) J. Biol. Chem. 271, 6686-6693) as being important for the formation, of a GalNAc-selective binding site.

==About this Structure==
1AFB is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Rattus_norvegicus Rattus norvegicus] with NGA, CA and CL as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1AFB OCA]. 

==Reference==
Structural basis of galactose recognition by C-type animal lectins., Kolatkar AR, Weis WI, J Biol Chem. 1996 Mar 22;271(12):6679-85. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=8636086 8636086]
[[Category: Rattus norvegicus]]
[[Category: Single protein]]
[[Category: Kolatkar, A.R.]]
[[Category: Weis, W.I.]]
[[Category: CA]]
[[Category: CL]]
[[Category: NGA]]
[[Category: c-type lectin]]
[[Category: calcium-binding protein]]

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