Hybrid cluster protein (HCP), formerly known as prismane, is thought to play a role in nitrogen metabolism but its specific function is unknown. HCP has three structural domains, an N-terminal alpha-helical domain, and two similar domains comprising a central beta-sheet flanked by alpha-helices. HCP contains two iron-sulfur clusters, one of which is a [Fe4-S4] cubane cluster similar to that of carbon monoxide dehydrogenase (CODH). The second cluster, referred to as the hybrid cluster, is a hybrid [Fe4-S2-O2] center located at the interface of the three domains. Although the hybrid cluster is buried within the protein, it is accessible through a large hydrophobic cavity.
Jiyao W et al.(2023). "The conserved domain database in 2023.",