Fig. 4
From: Design and structural characterisation of olfactomedin-1 variants as tools for functional studies
High-resolution crystal structure of Olfm1Olf to 1.25 Å with bound Na+ and Ca2+ ions reveals a structured switch loop and a water tunnel running to the metal ion binding sites. a Overview of the Olfm1Olf β-propeller domain with the bound Na+ (purple) and Ca2+ (green) ions. The switch loop is indicated in violet, the water tunnel in green, the hydrophobic plug residues closing the tunnel in dark red and individual water molecules in the tunnel are represented as red spheres. The intra-chain disulfide between Cys227 and Cys409 is shown in sticks representation. b Close-up of the metal ion binding site with 2Fo-Fc electron density contoured at 2.5 σ. Metal ion-coordinating interactions are shown as black dashes and the hydrogen bond of the coordinating carboxylic acid group of Asp356 with the hydroxyl group of Tyr347 in the switch loop is indicated in green. c Analysis of the tunnel radius by HOLE [48]