Protein∶co-factor and protein tetramerization contacts.

aAtom CBB is the terminal vinyl methylene carbon of pyrrole ring b, and atom CMA is the methyl carbon of pyrrole ring a (see Figure 4D for pyrrole naming within the heme protoporphyrin ring). Atoms O1A, O2A, and O1D are carboxylate oxygens of the propionate substituents of rings a and d, respectively.bAll the interactions between molecule 1 and molecule 2 are symmetric. Distances 1-2 and 2-1 are given separated by a slash.cAll the interactions between molecule 1 and molecule 3 are symmetric and made by identical atoms.