Halocyanin is an archaea blue (type I) copper redox protein
Halocyanins are blue (type I) copper redox proteins found in halophilic archaea such as Natronomonas pharaonis (Natronobacterium pharaonis). Halocyanin may serve as a mobile electron carrier at a peripheral membrane protein. The copper-binding domain is present only once in some halocyanins and is duplicated in others.