Mechanistic insights into Staphylococcus aureus IsdG-Ferrochelatase interactions: A key to understanding haem homeostasis in pathogens

In this study, we explore the molecular interactions between two Staphylococcus aureus enzymes, the haem oxygenase IsdG and ferrochelatase CpfC. Based on our previous research showing that IsdG interacts specifically with ferrochelatase, we constructed several mutants of IsdG and determined by fluorescence anisotropy the kinetic and affinity parameters of the interaction between CpfC and IsdG mutants. Our data indicate that the interacting residues on CpfC are located on a surface region distant from the porphyrin binding pocket. The identified interactions suggest that the inhibition of CpfC's iron-coproporphyrin chelatase activity by IsdG arises from long-range interactions, rather than direct blocking of the active site. Altogether, the experimental data allowed defining the regions involved in the interaction between the two proteins. These findings illuminate the interplay between haem acquisition and biosynthesis in pathogens, emphasizing the importance of specific protein interactions in mitigating intracellular haem toxicity. By elucidating these molecular mechanisms, we advance our understanding of bacterial haem homeostasis and contribute to development of potential therapeutic targets for combating haem-dependent pathogenesis.