Crystal Structure of a Viral FLIP: INSIGHTS INTO FLIP-MEDIATED INHIBITION OF DEATH RECEPTOR SIGNALING.
Li, F.-Y., Jeffrey, P.D., Yu, J.W., Shi, Y.(2006) J Biol Chem 281: 2960-2968
- PubMed: 16317000 
- DOI: https://doi.org/10.1074/jbc.M511074200
- Primary Citation of Related Structures:  
2F1S - PubMed Abstract: 
Death receptor signaling is initiated by the assembly of the death-inducing signaling complex, which culminates in the activation of the initiator caspase, either caspase-8 or caspase-10. A family of viral and cellular proteins, known as FLIP, plays an essential role in the regulation of death receptor signaling. Viral FLIP (v-FLIP) and short cellular FLIP (c-FLIPS) inhibit apoptosis by interfering with death receptor signaling. The structure and mechanisms of v-FLIP and c-FLIPS remain largely unknown. Here we report a high resolution crystal structure of MC159, a v-FLIP derived from the molluscum contagiosum virus, which is a member of the human poxvirus family. Unexpectedly, the two tandem death effector domains (DEDs) of MC159 rigidly associate with each other through a hydrophobic interface. Structure-based sequence analysis suggests that this interface is conserved in the tandem DEDs from other v-FLIP, c-FLIPS, and caspase-8 and -10. Strikingly, the overall packing arrangement between the two DEDs of MC159 resembles that between the caspase recruitment domains of Apaf-1 and caspase-9. In addition, each DED of MC159 contains a highly conserved binding motif on the surface, to which loss-of-function mutations in MC159 map. These observations, in conjunction with published evidence, reveal significant insights into the function of v-FLIP and suggest a mechanism by which v-FLIP and c-FLIPS inhibit death receptor signaling.
Organizational Affiliation: 
Department of Molecular Biology, Princeton University, Lewis Thomas Laboratory, Princeton, New Jersey 08544, USA.