Figure 4.

SRCR domain of SCARA1 recognizes cellular spectrin specifically. A, diagram of the domain arrangement of the α-chain of human spectrin. The fragments (F1, F2, and F3) expressed for binding assays are labeled. B, ELISAs show the binding of the spectrin fragments to hSCARA1. Sumo is applied as a control. C, dot-blot assays show the binding of spectrin F1 fragment to the SRCR and the CL–SRCR fragments of mSCARA1 or hSCARA1, whereas the F1 fragment has no detectable binding to the CC–CL fragment of SCARA1. SCARA1 fragments were spotted onto nitrocellulose membranes, and then the spectrin F1 fragment was incubated with the membranes in the binding buffer, including Ca²⁺ or EDTA. Anti-GFP or anti-spectrin antibodies were used for detection. Similar procedures were followed for F2 (D) and F3 (E) fragments. D, dot-blot assays show the binding of spectrin F2 fragment to the SRCR and the CL–SRCR fragments of mSCARA1 or hSCARA1, whereas the F2 fragment has no detectable binding to the CC–CL fragment of SCARA1. E, dot-blot assays show the binding of spectrin F3 fragment to the SRCR and the CL–SRCR fragments of mSCARA1 or hSCARA1, whereas the F3 fragment has no detectable binding to the CC–CL fragment of SCARA1. F, spectrin fragments (F1, F2, and F3) block the binding of the CL–SRCR fragment of mSCARA1 to dead cells. Sumo is applied as a control. G, spectrin fragments (F1, F2, and F3) block the binding of the CL–SRCR fragment of hSCARA1 to dead cells.