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Figure 5
(a) The N-terminal domain of each PPD1 subunit comprises two β-sheets formed from seven β-strands and encompasses residues 1–150. The first 20 residues were not modelled in the structure as they were not visible in the electron-density maps. (b) The PPD1 N-terminal end (green) aligned with the structure of the fibronectin type III domain of human sidekick-2 (PDB entry 1wfn ; Z = 4.6, r.m.s.d. = 2.99 Å, 76 aligned residues, chain A), an s-type immunoglobulin. The same orientation as in (a) is shown in the left panel and that with the view rotated about the vertical axis by 90° is shown in the right panel. A portion of the N-terminal loop of PDB entry 1wfn occluding the view has been omitted for clarity. (c) The same viewpoints are shown for the PPD1 N-terminal end (green) aligned with the structure of the antitumour antibiotic C-1027 apoprotein (PDB entry 1j48 ; Z = 5.9, r.m.s.d. = 2.04 Å, 80 aligned residues, chain A), which is a v-type immunoglobulin. The seven β-strands in PPD1 all have corresponding well aligned counterparts in the nine-stranded 1j48 structure. The `extra' hairpin β-strands are replaced by a short loop in PPD1. The enediyne chromophore in the holo form of C-1027 is bound at a hydrophobic pocket, the position of which is indicated by the arrow.

Volume 1| Part 2| February 2014| Pages 101-109
ISSN: 2052-2525