FIGURE 3.

Analysis of CLDN1-CD81 extracellular loop interactions by surface plasmon resonance. MBP-CLDN1 EC1 (A) and MBP-CD81 EC2 (B and C) were immobilized onto the bio-sensor chip surface. Homotypic protein interactions were demonstrated by flowing MBP-CLDN1 EC1 (solid gray line) and MBP-CD81 EC2 (solid black line) over the respective chip surfaces (A and B) with both MBP-CLDN7 EC1 (dotted light gray line) and MBP (dotted black line) as negative controls at a concentration of 1 mg/ml. Heterotypic interaction between MBP-CLDN1-EC1 and MBP-CD81 EC2 is depicted in C. To control for nonspecific interactions, all MBP fusion proteins were flowed over an activated and blocked “empty” channel, and the response unit(s) were subtracted from the test channels. The arrow indicates the “association time” i when proteins are flowed over the respective chip surfaces and the “dissociation phase” begins at time ii when protein injection is stopped. Data are representative of two independent experiments.