Two-step adhesive binding by classical cadherins.
Crystal structures of classical cadherins have revealed two dimeric configurations. In the first, N-terminal beta-strands of EC1 domains 'swap' between partner molecules. The second configuration (the 'X dimer'), also observed for T-cadherin, is mediated by residues near the EC1-EC2 calcium binding sites, and N-terminal beta-strands of partner EC1 domains, though held adjacent, do not swap. Here we show that strand-swapping mutants of type I and II classical cadherins form X dimers. Mutant cadherins impaired for X-dimer formation show no binding in short-time frame surface plasmon resonance assays, but in long-time frame experiments, they have homophilic binding affinities close to that of wild type. Further experiments show that exchange between monomers and dimers is slowed in these mutants. These results reconcile apparently disparate results from prior structural studies and suggest that X dimers are binding intermediates that facilitate the formation of strand-swapped dimers.
Harrison
Oliver J
OJ
Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York, USA.
Bahna
Fabiana
F
Katsamba
Phini S
PS
Jin
Xiangshu
X
Brasch
Julia
J
Vendome
Jeremie
J
Ahlsen
Goran
G
Carroll
Kilpatrick J
KJ
Price
Stephen R
SR
Honig
Barry
B
Shapiro
Lawrence
L
D000818:Animals; D016466:CHO Cells; D015820:Cadherins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002448:Cell Adhesion / Q000502:physiology; D006224:Cricetinae; D003412:Cricetulus; D009154:Mutation; D011485:Protein Binding / Q000502:physiology; D055503:Protein Multimerization / Q000235:genetics / Q000502:physiology; D017433:Protein Structure, Secondary; D020349:Surface Plasmon Resonance; D014461:Ultracentrifugation
D015820:Cadherins