Fig. 2. Stereo view of putative binding site and cavities. The cavities as calculated by GRASP (Nicholls et al., 1991) are shown in different colors. Cavities shown in blue and green are at the top of the molecule away from the membrane surface. Residues forming these cavities are shown as a stick model in corresponding colors. Each cavity has a volume of 50 Å³ and is formed by residues Ala75, Ile76, Gly77, Lys78, Lys79, Glu89, Ala90, Asp91, His92 and Asn93 of one monomer, and Gly94, Ser95, Ser98, Gly146, Lys147 and Glu148 of the other monomer. The solvent structures in the cavities are remarkably well conserved between the HB19 and B31 molecules.