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Mapping of the laminin‐binding site of the N‐terminal agrin domain (NtA)
Author(s) -
Mascarenhas Joseph B.,
Rüegg Markus A.,
Winzen Uwe,
Halfter Willi,
Engel Jürgen,
Stetefeld Jörg
Publication year - 2003
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/cdg041
Subject(s) - agrin , heptad repeat , laminin , biology , coiled coil , binding site , biophysics , biochemistry , plasma protein binding , basal lamina , protein structure , mutagenesis , site directed mutagenesis , acetylcholine receptor , microbiology and biotechnology , peptide sequence , mutant , receptor , anatomy , gene , ultrastructure , cell
Agrin is a key organizer of acetylcholine receptor (AChR) clustering at the neuromuscular junction. The binding of agrin to laminin is required for its localization to synaptic basal lamina and other basement membranes. The high‐affinity interaction with the coiled‐coil domain of laminin is mediated by the N‐terminal domain of agrin. We have adopted a structurally guided site‐directed mutagenesis approach to map the laminin‐binding site of NtA. Mutations of L117 and V124 in the C‐terminal helix 3 showed that they are crucial for binding. Both residues are located in helix 3 and face the groove between the β‐barrel and the C‐terminal helical segment of NtA. Remark ably, the distance between both residues matches a heptad repeat distance of two aliphatic residues which are solvent exposed in the coiled‐coil domain of laminin. A lower but significant contribution originates from R43 and a charged cluster (E23, E24 and R40) at the open face of the β‐barrel structure. We propose that surface‐exposed, conserved residues of the laminin γ1 chain interact with NtA via hydrophobic and ionic interactions.

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