This old version of Proteopedia is provided for student assignments while the new version is undergoing repairs. Content and edits done in this old version of Proteopedia after March 1, 2026 will eventually be lost when it is retired in about June of 2026.
Apply for new accounts at the new Proteopedia. Your logins will work in both the old and new versions.
2oz4
From Proteopedia
Structural Plasticity in IgSF Domain 4 of ICAM-1 Mediates Cell Surface Dimerization
Contents |
Overview
The Ig superfamily (IgSF) intercellular adhesion molecule-1 (ICAM-1) equilibrates between monomeric and dimeric forms on the cell surface, and dimerization enhances cell adhesion. A crystal structure of ICAM-1 IgSF domains (D) 3-5 revealed a unique dimerization interface in which D4s of two protomers fuse through edge beta-strands to form a single super beta-sandwich domain. Here, we describe a crystal structure at 2.7-A resolution of monomeric ICAM-1 D3-D5, stabilized by the monomer-specific Fab CA7. CA7 binds to D5 in a region that is buried in the dimeric interface and is distal from the dimerization site in D4. In monomeric ICAM-1 D3-D5, a 16-residue loop in D4 that is disordered in the dimeric structure could clearly be traced as a BC loop, a short C strand, and a CE meander with a cis-Pro followed by a solvent-exposed, flexible four-residue region. Deletions of 6 or 10 residues showed that the C-strand is essential for monomer stability, whereas a distinct six-residue deletion showed little contribution of the CE meander. Mutation of two inward-pointing Leu residues in edge beta-strand E to Lys increased monomer stability, confirming the hypothesis that inward-pointing charged side chains on edge beta-strands are an important design feature to prevent beta-supersheet formation. Overall, the studies reveal that monomer-dimer transition is associated with a surprisingly large, physiologically relevant, IgSF domain rearrangement.
Disease
Known disease associated with this structure: Malaria, cerebral, susceptibility to OMIM:[147840]
About this Structure
2OZ4 is a Single protein structure of sequence from Homo sapiens and Mus musculus. Full crystallographic information is available from OCA.
Reference
Structural plasticity in Ig superfamily domain 4 of ICAM-1 mediates cell surface dimerization., Chen X, Kim TD, Carman CV, Mi LZ, Song G, Springer TA, Proc Natl Acad Sci U S A. 2007 Sep 25;104(39):15358-63. Epub 2007 Sep 19. PMID:17881562 Page seeded by OCA on Sun May 4 11:58:15 2008
