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. 2011 Jun 6;10(9):M111.009787. doi: 10.1074/mcp.M111.009787

Fig. 1.

Fig. 1.

ESI-MS spectra of p2 baseplates and sub-complexes. A, p2 baseplate (BP1). The measured mass of the intact complex centered at m/z 14,000 (red circles) is 862,727 Da, consistent with a stoichiometry of [6×ORF15 + 3×ORF16 + 18×ORF18]. Also present are ORF18 trimers (blue circles; 88,015 Da) and an [3× ORF18 + ORF15] complex (yellow circles; 122,499 Da). B, p2 baseplate in complex with the VHH5 llama antibody (BP2). Signals for the p2 baseplate complex with 18 VHH domains [6×ORF15 + 3×ORF16 + 18×ORF18 + 18×VHH5] are centered at m/z 15,000 with a measured mass of 1,114,961 Da (green circles; the inset shows a x42 magnification of this m/z region). VHH5 monomer can also be identified (magenta circles; m/z 3000; 13,913 Da). C, p2 baseplate subcomplex SBP1 [6×ORF15 + 3×ORF16]; 354,862 Da) centered at m/z 8500 (gray triangles). Also identified are a species corresponding to the dimer of SBP1 (m/z 12,000; red triangles), ORF16 monomers (42,838 Da), dimers and trimers (navy blue, green, and yellow triangles at m/z 3500, 4500, and 5500, respectively), and ORF15 monomer (37,724 Da) (pale blue triangles; m/z 3000). An ORF15 truncation product is observed (35,965 Da; m/z 3000; orange triangles), which is consistent with the loss of the first 15 C-terminal residues. D, p2 baseplate sub-complex SBP2 showing ORF18 trimers (88,015 Da) (blue stars; m/z 4500) and the [3×ORF18 + ORF15] complex with a mass of 122,508 Da (orange stars; m/z 5500). Both species are accompanied by the corresponding complexes containing a truncated ORF18 sub-unit.