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Figure 3.
Figure 3. Structure of the chagasin-cathepsin L complex. (a)
A ribbon stereodiagram of the complex. The inhibitor molecule is
colored gold and the enzyme blue. The surfaces of both proteins
are marked in an analogous way. The view corresponds to the
standard orientation used for cysteine proteases, along the
interface between the left (L) and right (R) domains forming the
sides of the active site cleft of cathepsin L. (b) Interaction
of chagasin in the catalytic cleft of cathepsin L, viewed
perpendicular to the standard orientation, with the L-domain
behind the inhibitor molecule and the R-domain in the front. The
side-chains of residues crucial for enzyme interactions are
represented by sticks and balls (the disordered side-chain of
K63 is shown in both alternative conformations) The enzyme is
colored blue and the framework inhibitor molecule gold, with the
enzyme-interacting loops L4, L2 and L6 in light yellow, orange
and gold, respectively. (c)–(e) Details of the enzyme
interactions of loops (c) L2, (d) L4 and (e) L6. In (c),
side-chains of the interacting residues are shown in
2F[o]–F[c] electron density contoured at the 1.2ó
level, to illustrate its quality.
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