Relative structural positioning of the hub residues, mutated residues and the active site of Sfβgly (5CG0; [17]).

<p>Residues D260 to E265 and L335 to S337, which are close to the hub residue F251, were submitted to site-directed mutagenesis. F251, N249, S247 and T245 are hub residues. E187 and E399 are the catalytic acid and nucleophile, respectively. For clarity, only the side chains are shown, some secondary elements were removed and panels A and B are shown in different perspectives. <b>A</b>–The hub residues F251, N249, S247 and T245 form a pathway connecting the mutation sites near the protein surface to the core and active site of Sfβgly. The shortest distances are: F251_Cε –N249_Cβ: 4.1 Å; N249Nδ2 –S247_Oλ: 3.9 Å; S247_Cβ-T245_Cβ: 7.7 Å; F251_Cβ –A264_Cβ: 5.3 Å; A264_Cβ - A263_Cβ: 5.3 Å. These contacts, except those involving T245, are within the distance limits for noncovalent interactions (<i>i</i>.<i>e</i>., 5 Å). <b>B</b>–A different perspective of the mutated residues A263, A264, V336 and S337, which are close to the hub residue F251. The side chains are shown as spheres highlighting the clustering of A263, A264, V336, S337 and F251. The contact distances are near to the upper limit (5 Å) for non-covalent interactions (F251_Cβ –V336_Cλ: 4 Å; F251_Cβ –A264_Cβ: 5.3 Å; A264_Cβ –A263_Cβ: 5.3 Å). Residues M262, E265 and T335, sites of innocuous mutations, do not take part of this cluster.