journal menu
![[Figure 2]](nz5009fig2mag.jpg)
|
|
Figure 2
Structural features of pLAST. (a) Ribbon-type plot of the PP (blue ribbon) and the CD (orange/red ribbon) of the Limulus astacin zymogen in cross-eyed stereo. The regular secondary-structure elements (helices α1–α8 in blue/brick and β-strands β1–β7 in orange) are depicted and labelled, as are the N-terminus and the C-terminus. The activation cleavage site K48–N49 is pinpointed by a green arrow and the catalytic zinc is pictured as a purple sphere. Residues engaged in zinc binding are shown with their side chains as sticks and labelled (D38 in blue; H139, H143 and H149 in red; Y198 in green), as are the Met-turn methionine (M196 in green), the general base/acid glutamate (E140) mutated to alanine (in red) and the two disulfide bonds (yellow; 1, C90–C244; 2, C112–C131). (b) Structure of the zymogen showing the electrostatic surface of the CD and the PP as a pale blue ribbon traversing the deep and extended active-site cleft in the reverse direction to a substrate. The side chain of the `aspartate-switch' residue D38 is shown and labelled. (c) Close-up view of (a) depicting the distorted octahedral coordination sphere of the catalytic zinc ion. The Nɛ2 atoms of H139 and H149 as well as the Oδ1 and Oδ2 atoms of D38 lie in a plane with the metal. The H143 Nɛ2 and, more distantly, Y198 Oη atoms occupy the apical positions. The Met-turn, which includes M196, is pictured as a cyan ribbon and labelled. |
![[Figure 2]](nz5009fig2.jpg)
 | STRUCTURAL BIOLOGY |
ISSN: 2059-7983
Open 
access
access
