Lateral self‐assembly of E‐cadherin directed by cooperative calcium binding

FEBS Letters

Porumb, Tudor³  Alattia, Jean-René³  Kay, Cyril M.¹  Ames, James B.²  Ottensmeyer, Peter³  Tong, Kit I.³  Ikura, Mitsuhiko³  Heng, Yew Meng³ 

[1] Department of Biochemistry and the Protein Engineering Network of Centre of Excellence, University of Alberta, Edmonton, Alta. T6G 2H7, Canada;Department of Neurobiology, Stanford University School of Medicine, Stanford, CA 94305, USA;Division of Molecular and Structural Biology, Ontario Cancer Institute and Department of Medical Biophysics, University of Toronto, 610 University Avenue, Toronto, Ont. M5G 2M9, Canada

关键词: Cell adhesion;    Cadherin;    Calcium;    Dimerization;   

DOI  :  10.1016/S0014-5793(97)01333-1

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

We report the Ca²⁺ binding characteristics of recombinant Ecad12, a construct spanning the first two repeats of epithelial cadherin, and demonstrate the links between Ca²⁺ binding and dimer formation. Sedimentation equilibrium and dynamic light scattering experiments show that weak dimerization of Ecad12 occurs in the presence of 10 mM Ca²⁺ (K ^P _d=0.17 mM), while no appreciable dimer formation was detected in the absence of Ca²⁺. Ca²⁺-induced dimerization was also observed in electron microscopy images of Ecad12. We conclude from Ca²⁺ titration experiments monitored by tryptophan fluorescence and flow dialysis that dimerization does not affect the equilibrium binding constant for Ca²⁺. However, the value of the Hill coefficient for Ca²⁺ binding increases from 1.5 to 2.4 as the protein concentration increases, showing that dimer formation largely contributes to the cooperativity in Ca²⁺ binding. Based on these observations and previous crystallographic studies, we propose that calcium acts more likely as a geometrical aligner ensuring the proper assembly of cadherin molecules, rather than a simple adhesive.

【 授权许可】

Unknown