Figure 4
Ribonucleolytic site of ZmASCH. (a) Simulated ZmASCH structure in complex with an ssRNA AGGACAU. The ZmASCH apo-structure and two representative simulated complex structures were superimposed. Three protein structures were displayed with coils of different colors. The bound ssRNA is depicted as blue lines; 5′- and 3′-ends are labeled. Some key residues that interact with ssRNA, which were mutated, are depicted as stick models. (b,c) Interaction of ZmASCH with an ssRNA at two sites. The bound ssRNA (cyan-colored carbon) and the protein residues (green-colored carbon) were drawn as thick stick models. Water molecules are displayed as red spheres and polar interactions among atoms are indicated with black-dotted lines. (d) 32P-labelled RNA or DNA probes (0.3 μM) were incubated with wild-type and mutant proteins of ZmASCH (3 μM) for 30 min at 310 K in the presence of 10 mM MgCl2. The bracket on the left panel indicates the degradation products.
