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Fig. 7 | BMC Evolutionary Biology

Fig. 7

From: Lacking catalase, a protistan parasite draws on its photosynthetic ancestry to complete an antioxidant repertoire with ascorbate peroxidase

Fig. 7

Homology models of PmAPX1, PmAPX2 and predicted APX proteins from Oxyrrhis, Amphidinium, and Vitrella. a Ribbon diagrams, illustrating a high degree of conserved alpha helix structure above the heme plane and along the plane edges. Below the heme plane the models diverge and there is less helical structure. Apertures to the heme group through equatorial gaps in the modeled surface are visible in this view. The top left structure is a heme molecule diagram with alpha, beta, delta and gamma edges labeled. b The active site of PmAPX1 and PmAPX2, showing conserved structure and residues. Left: Ribbon diagrams showing the residues in the vicinity of the heme (Carbon: yellow; Nitrogen: blue; Oxygen: red). Right: The heme group and nearby residues are shown without the peptide backbone. The conserved residues Trp-His-Arg-Asp above the heme and Ser-His-Trp-Asp below the heme are labeled (Carbon: light blue; Nitrogen: blue; Oxygen: red). The Phe residue (173 in APX1, 205 in APX2) (Carbon: green; Nitrogen: blue; Oxygen: red) at the gamma heme edge is conserved between PmAPX1, PmAPX2 and the APX of dinoflagellates, but not in plants or Vitrella (where the corresponding residue is His or Arg, see Additional file 4: Figure S3)

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