1ie5
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(New page: 200px<br /><applet load="1ie5" size="450" color="white" frame="true" align="right" spinBox="true" caption="1ie5" /> '''NMR STRUCTURE OF THE THIRD IMMUNOGLOBULIN DO...)
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Revision as of 15:12, 20 November 2007
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NMR STRUCTURE OF THE THIRD IMMUNOGLOBULIN DOMAIN FROM THE NEURAL CELL ADHESION MOLECULE.
Overview
Homophilic binding of the neural cell adhesion molecule (N-CAM) mediates, the calcium-independent cell-cell adhesion that is involved in neuronal, development. Two hypotheses have been advanced for the mechanism of, homophilic binding. Cell-based experiments have implicated each of the, five extracellular immunoglobulin (Ig) domains of N-CAM in the homophilic, adhesion interaction, and have predicted that the third domain (Ig III), self-associates. The alternative hypothesis is based on solution, observations, which implicate a specific antiparallel interaction between, the first two Ig domains (Ig I and Ig II). In order to test these, hypotheses, we have determined a high-resolution solution structure of, recombinant Ig III (sequence derived from chicken N-CAM) and examined the, aggregation behavior of isolated Ig domains in solution. The structure, shows that Ig III adopts a canonical Ig fold, in which the beta strands, ABED and A'GFCC' form two beta sheets that are linked by a disulfide bond., In contrast to the demonstrated aggregation of Ig III on solid supports, we were unable to demonstrate self-association of Ig III under any of a, variety of solution conditions. The structure shows that the surface of Ig, III is dominated by two large acidic patches, which may explain our, failure to observe self-association in solution. To evaluate the, involvement of the Ig I-Ig II interaction in cell-cell adhesion, we, designed a point mutation in Ig I (F19S) that proved sufficient to, abrogate the Ig I-Ig II interaction seen in solution. However, the, introduction of this mutation into full-length N-CAM expressed in COS-7, cells failed to affect N-CAM-mediated cell-cell adhesion. The inability to, observe Ig III self-association in solution, combined with the failure of, the F19S mutation to affect N-CAM-mediated cell-cell adhesion, suggests, that, although solution studies can give important insights into the, structures of individual domains, the interactions observed in solution, between the domains may not be representative of the interactions that, occur on the cell surface.
About this Structure
1IE5 is a Single protein structure of sequence from Gallus gallus. Full crystallographic information is available from OCA.
Reference
Solution structure of the third immunoglobulin domain of the neural cell adhesion molecule N-CAM: can solution studies define the mechanism of homophilic binding?, Atkins AR, Chung J, Deechongkit S, Little EB, Edelman GM, Wright PE, Cunningham BA, Dyson HJ, J Mol Biol. 2001 Aug 3;311(1):161-72. PMID:11469865
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