<p>Some fungal transcription factors contain an N-terminal domain, the copper fist,which seems to be involved in copper-dependent DNA-binding [<cite idref="PUB00001242"/>, <cite idref="PUB00002782"/>].These proteins activate the transcription of the metallothionein gene in response tocopper. Metallothionein maintains copper levels in yeast [<cite idref="PUB00006077"/>, <cite idref="PUB00001242"/>]. The copper fist domain, which is similar in structure to metallothionein itself, undergoesa large conformational change on copper-binding that allows DNA-binding. The domain contains a conserved array of zinc-binding residues (Cys-X2-Cys-X8-Cys-X-His) and forms a three-stranded antiparallel beta-sheet with two short helical segments that project from one end of the beta-sheet [<cite idref="PUB00016288"/>]. Conserved residues form a basic patch that may be important for DNA binding. </p>