Figure 1.

Location of key residues that interact with the heme and PLP in hCBS. Labeled are: the Fe(III) heme ligands Cys⁵² and His⁶⁵; the cysteine(thiolate) hydrogen bonding partners Arg²⁶⁶ and the amide backbone of Trp⁵⁴; the PLP phosphate hydrogen bonding partners Thr²⁵⁷ and Thr²⁶⁰; and the PLP internal aldimine forming Lys¹¹⁹. Data taken from PDB file 1JBQ (14). The polypeptide backbone is colored using a rainbow scheme from N-terminus (blue) to C-terminus (red).