Mechanism of E-cadherin dimerization probed by NMR relaxation dispersion.
Epithelial cadherin (E-cadherin), a member of the classical cadherin family, mediates calcium-dependent homophilic cell-cell adhesion. Crystal structures of classical cadherins reveal an adhesive dimer interface featuring reciprocal exchange of N-terminal β-strands between two protomers. Previous work has identified a putative intermediate (called the "X-dimer") in the dimerization pathway of wild-type E-cadherin EC1-EC2 domains, based on crystal structures of mutants not capable of strand swapping and on deceleration of binding kinetics by mutations at the X-dimer interface. In the present work, NMR relaxation dispersion spectroscopy is used to directly observe and characterize intermediate states without the need to disrupt the strand-swapped binding interface by mutagenesis. The results indicate that E-cadherin forms strand-swapped dimers predominantly by a mechanism in which formation of a weak and short-lived X-dimer-like state precedes the conformational changes required for formation of the mature strand-swapped dimeric structure. Disruption of this intermediate state through mutation reduces both association and dissociation rates by factors of ~10(4), while minimally perturbing affinity. The X-dimer interface lowers the energy barrier associated with strand swapping and enables E-cadherins to form strand-swapped dimers at a rate consistent with residence times in adherens junctions.
Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, and Edward S. Harkness Eye Institute, Columbia University, New York, NY 10032.
Ying
Y
Li
Nicole L
NL
Altorelli
Fabiana
F
Bahna
Barry
B
Honig
Lawrence
L
Shapiro
Arthur G
AG
Palmer
D000818:Animals; D015820:Cadherins / Q000737:chemistry*; D002448:Cell Adhesion / Q000502:physiology*; D019281:Dimerization; D005453:Fluorescence; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D051379:Mice; D008958:Models, Molecular; D011487:Protein Conformation
D015820:Cadherins
binding mechanism; domain swapping; protein-protein interaction