Dependence of CDHR3 and C15 binding on calcium.

Lysates transfected with cDNAs encoding Y529 CDHR3 protein were reacted with C15 virus in buffer with 2mM calcium, 2mM EDTA or EGTA (A), or in calcium-free buffer (B) and immunoprecipitated with an α-CDHR3 mAb reactive with the cytoplasmic domain. (C) Purified rEC1-3 protein (100 pmol) was reacted with C15 virus in buffer with 2mM CaCl₂ or 2 mM EDTA or EGTA. (D) rEC1-3, rEC1-2, and rEC1 (100 pmol) protein were first reacted with C15 virus in buffer with or without 2 mM CaCl₂ for 1 h at 25 and then incubated another 2 hrs following the addition of 5 mM CaCl₂ to designated samples. Immunoprecipitation was with an α-His mAb. Each panel (ABCD) is a separate experiment. Binding % is the observed C15 signal pixel count normalized to the CDHR3 protein (α-His) signal in the panel above (Total Lab 100) relative to positive control (100) in each unit.