Differences between PYP molecules. (A) Cα rmsds after pairwise superpositions of the A and B chains (blue; mean rmsd, 0.28 Å), C and B chains (red; mean rmsd, 0.34 Å), A and C chains (green; mean rmsd, 0.42 Å), and E-PYP and B chain (cyan; mean rmsd, 0.80 Å). Those deviations >0.96 Å (thin black line) are considered to be statistically significant. (B) Superposition of B chain of Ppr-PYP (red) and E-PYP (blue). The N and C termini, the Cys-69 required for chromophore attachment, and the three loops that have statistically significant differences between E-PYP and Ppr-PYP are labeled.