Investigation of the three dimensional models of Kex2, furin and Kumamolisin for substrate binding properties. (A) Superimposed 3D coordinate sets for the three proteases reveal colocalization of the Kumamolisin propeptide residues with the predicted S1' and S2' binding pockets in furin and Kex2. A region identified for binding of the inhibitor Eglin-c (purple)  is not involved in binding of the propeptide. (B) and (C) A potential S4' binding pocket is identified which is terminated by H369 in Kex2 and E262 in furin. Numbering "a" through "E" refers to residues used in Table 2, which lists the respective binding pockets and references.