Fig. 1. Design and expression of soluble receptor proteins. Scheme of intercellular adhesion molecule-1 (IC1) and poliovirus receptor (PVR). IgSF domains are labeled D1–D5 or D1–D3, and the transmembrane domain is represented by a black rectangle. Cysteine residues are indicated with ‘S’ and glycosylation sites with ‘lollipop’ representations. Arrows indicate positions in which the engineered translation stop codon (*) was introduced to generate the two-domain variants. Stop codons are located after residues Thr190 of the mature IC1 and after Leu238 and Tyr241 of the precursor PVR polypeptide (see Materials and methods). The inset shows silver-stained 10% SDS–PAGE of purified soluble IC1-2D (left) and PVR-2D (right) proteins. The position and size (kDa) of molecular weight markers are included.