Figure 5.

Two examples of dioxane (Dio) molecules binding to subtilisin Carlsberg in anhydrous dioxane. (A) A dioxane molecule is seen interacting with Pro-5, Tyr-6, Gly-204, Val-205, Tyr-206, and a water molecule and with Ala-52 and Gly-53 of one neighboring symmetry-related subtilisin molecule, as well as Tyr-256 of another. (All residues depicted are within 3.5 Å of the dioxane.) (B) A dioxane molecule is displayed interacting with Phe-50, Ser-109, Glu-112, and a water molecule and with Pro-210 and Thr-213 of a neighboring subtilisin molecule. In both A and B, the central subtilisin’s residues and bound solvent molecules mentioned above are displayed as balls-and-sticks where the carbon, oxygen, and nitrogen are white, light-gray, and black, respectively; the ribbon diagram of the subtilisin backbone is also white. The neighboring symmetry-related subtilisin’s residues and ribbons are shown in darker gray colors. The hydrogen bonds, in which the dioxane oxygen atoms could be involved, are shown as gray dashed lines.