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.