title: Vaccinia virus protein A49 is an unexpected member of the B-cell Lymphoma (Bcl)-2 protein family.
abstract: Vaccinia virus (VACV) encodes several proteins that inhibit activation of the proinflammatory transcription factor nuclear factor κB (NF-κB). VACV protein A49 prevents translocation of NF-κB to the nucleus by sequestering cellular β-TrCP, a protein required for the degradation of the inhibitor of κB. A49 does not share overall sequence similarity with any protein of known structure or function. We solved the crystal structure of A49 from VACV Western Reserve to 1.8 Å resolution and showed, surprisingly, that A49 has the same three-dimensional fold as Bcl-2 family proteins despite lacking identifiable sequence similarity. Whereas Bcl-2 family members characteristically modulate cellular apoptosis, A49 lacks a surface groove suitable for binding BH3 peptides and does not bind proapoptotic Bcl-2 family proteins Bax or Bak. The N-terminal 17 residues of A49 do not adopt a single well ordered conformation, consistent with their proposed role in binding β-TrCP. Whereas pairs of A49 molecules interact symmetrically via a large hydrophobic surface in crystallo, A49 does not dimerize in solution or in cells, and we propose that this hydrophobic interaction surface may mediate binding to a yet undefined cellular partner. A49 represents the eleventh VACV Bcl-2 family protein and, despite these proteins sharing very low sequence identity, structure-based phylogenetic analysis shows that all poxvirus Bcl-2 proteins are structurally more similar to each other than they are to any cellular or herpesvirus Bcl-2 proteins. This is consistent with duplication and diversification of a single BCL2 family gene acquired by an ancestral poxvirus.
authors.affiliation: From the Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, United Kingdom and.
authors.forename: Sarah
authors.initials: S
authors.lastname: Neidel
authors.affiliation: From the Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, United Kingdom and.
authors.forename: Carlos
authors.initials: C
authors.lastname: Maluquer de Motes
authors.affiliation: the Department of Microbiology, Immunology, and Parasitology, Universidade Federal de Santa Catarina, Florianopolis, 88040-900 Brazil.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Mansur
authors.affiliation: From the Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, United Kingdom and.
authors.forename: Pavla
authors.initials: P
authors.lastname: Strnadova
authors.affiliation: From the Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, United Kingdom and.
authors.forename: Geoffrey L
authors.initials: GL
authors.lastname: Smith
authors.affiliation: From the Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, United Kingdom and scg34@cam.ac.uk.
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Graham
mesh_terms: D017209:Apoptosis / Q000235:genetics; D018360:Crystallography, X-Ray; D057809:HEK293 Cells; D006801:Humans; D007113:Immunity, Innate / Q000235:genetics*; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D011487:Protein Conformation; D017510:Protein Folding; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics*; D014615:Vaccinia / Q000235:genetics / Q000821:virology; D014616:Vaccinia virus / Q000737:chemistry / Q000235:genetics / Q000472:pathogenicity; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics
chemical_list: D016328:NF-kappa B; D019253:Proto-Oncogene Proteins c-bcl-2; D014764:Viral Proteins
keywords: B-cell Lymphoma 2 (Bcl-2) Family; Innate Immunity; NF-κB (NF-KB); Poxvirus; Protein Structure; Structure-based Phylogenetics; Vaccinia Virus; Viral Protein