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Molecular modelling of the immunoglobulin‐like domains of the neural cell adhesion molecule (NCAM): Implications for the positioning of functionally important sugar side chains
Author(s) -
Santoni M.J.,
Goridis C.,
FontecillaCamps J. C.
Publication year - 1988
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/jnr.490200304
Subject(s) - neural cell adhesion molecule , immunoglobulin superfamily , immunoglobulin domain , cell adhesion , cell adhesion molecule , chemistry , sialic acid , biology , biophysics , microbiology and biotechnology , biochemistry , cell , receptor
The neural cell adhesion molecule (NCAM) is thought to mediate cell–cell adhesion by a homophilic mechanism involving binding sites located in the N‐terminal region of the protein. This region of the molecule consists of five domains that are homologous to each other and share conserved residues with immunoglobulin domains. We report here secondary structure predictions for the five NCAM domains and three‐dimensional models for two of them. The results are entirely consistent with an immunoglobulin‐like folding of the NCAM domains into seven strands forming two b̃‐sheets. NCAM–NCAM binding may thus be analogous to the pairwise associations of immunoglobulin constant domains, which are involved in dimer formation. Insertions and deletions are located mostly in b̃‐turn regions. Two α‐helical regions in the third and fourth domain are predicted with high probability. NCAM bears two kinds of functionally important sugar side chains, sialic acid polymers in the fifth domain, which modulate NCAM binding, and the L2 moiety, which is involved in cell adhesion and can be assigned to the third domain. Three‐dimensional modelling of the corresponding domains indicates that two of the three sites for N‐linked glycosylation in the fifth and the single site in the third domain are located on he face of the domain, which in immunoglobulin contant regions engages in intermolecular interactions.

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