Fig 1.
Identifying putative viral Bcl-2 (vBcl-2) homologs. (A) Using myxoma virus M11L as the query sequence in a BLASTP search of the NCBI database, six putative Bcl-2 family proteins encoded by viruses were identified (40). The pairwise identities (percent) in the amino acid sequences between the proteins were determined using ClustalW (57). Note the low sequence homology (<15%) of all the putative vBcl-2 proteins to human Bcl-xL. (B) The amino acid sequence of a vBcl-2, SPPV14, was structurally aligned with those of myxoma virus M11L (40), mouse Bcl-xL (44), and KSHV Bcl-2 (35). Based on this alignment, the residues making up α-helices 1 to 8 are marked “H.” The colored shading indicates the BH1 (magenta), BH2 (orange), BH3 (green), and BH4 (yellow) Bcl-2 homology regions in Bcl-xL and KSHV Bcl-2. The residues marked in cyan are those in the BH3 binding groove of M11L and conserved between it and SPPV14 (Fig. 2A). TM indicates the putative transmembrane region as taken from M11L.