Crystal structure of the <em>Clostridium limosum</em> C3 exoenzyme

C3-like toxins ADP-ribosylate and inactivate Rho GTPases. Seven C3-like ADP-ribosyltransferases produced by , , and were identified and two representatives – C3bot from and C3stau2 from – were crystallized. Here we present the 1.8Å structure of C3 transferase C3lim and compare it to the structures of other family members. In contrast to the structure of apo-C3bot, the canonical ADP-ribosylating turn turn motif is observed in a primed conformation, ready for NAD binding. This suggests an impact on the binding mode of NAD and on the transferase reaction. The crystal structure explains why auto-ADP-ribosylation of C3lim at Arg41 interferes with the ADP-ribosyltransferase activity of the toxin.

C3样毒素使ADP -核糖基化并使Rho GTP酶失活。已鉴定出由[具体生物名称缺失]、[具体生物名称缺失]、[具体生物名称缺失]和[具体生物名称缺失]产生的7种C3样ADP -核糖基转移酶，并且两种代表物——来自[具体生物名称缺失]的C3bot和来自[具体生物名称缺失]的C3stau2——已被结晶。在此我们展示了[具体生物名称缺失]C3转移酶C3lim的1.8Å结构，并将其与其他家族成员的结构进行比较。与脱辅基C3bot的结构相反，在引发构象中观察到典型的ADP -核糖基化转角基序，可随时与NAD结合。这表明对NAD的结合模式以及转移酶反应有影响。该晶体结构解释了为什么C3lim在Arg41处的自身ADP -核糖基化会干扰该毒素的ADP -核糖基转移酶活性。