<p>Halocyanins are blue (type I) copper redox proteins found in halophilic archaea such as <taxon tax_id="2257">Natronomonas pharaonis</taxon> (Natronobacterium pharaonis). Halocyanin from from N. pharaonis has been characterised <db_xref db="SWISSPROT" dbkey="P39442"/> and shown to be a small blue copper protein with a molecular mass of about 15.5 kDa [<cite idref="PUB00002847"/>, <cite idref="PUB00043429"/>]. This protein, which was named halocyanin, contains one Cu2+, with a copper-binding site containing two His, one Met, and one Cys as probable ligands. It is probable that halocyanin is a peripheral membrane protein, which serves as a mobile electron carrier.</p><p>This entry represents the copper-binding domain of halocyanins. This domain is present only once in some halocyanins and is duplicated in others. It is not found in plastocyanins or certain divergent paralogs of halocyanin.</p> Halocyanin