(a) Molecular modeling of the extracellular, soluble portion of rat FasL. The soluble rat FasL trimer fragment was visualized based on the structure of TNF-α . The Pt 86 FasL mutation is labeled in red and the hgld mutation is labeled in blue in side (left) and front (right) projections. The Pt 55C FasL mutation is not indicated in this model since it is located in the transmembrane domain, which is outside of the region in the model depicted. (b) A diagram of cloning strategy for epitope-tagging Fas-ligand protein.