<p>The ATP-cone is an evolutionarily mobile, ATP-binding regulatory domain which is found in a variety of proteins including ribonucleotide reductases, phosphoglycerate kinases and transcriptional regulators [<cite idref="PUB00007748"/>].</p><p>In ribonucleotide reductase protein R1 (<db_xref db="SWISSPROT" dbkey="P28903"/>) from <taxon tax_id="562">Escherichia coli</taxon> this domain is located at the N terminus, and is composed mostly of helices [<cite idref="PUB00005954"/>]. It forms part of the allosteric effector region and contains the general allosteric activity site in a cleft located at the tip of the N-terminal region [<cite idref="PUB00005953"/>]. This site binds either ATP (activating) or dATP (inhibitory), with the base bound in a hydrophobic pocket and the phosphates bound to basic residues. Substrate binding to this site is thought to affect enzyme activity by altering the relative positions of the two subunits of ribonucleotide reductase.</p> ATP-cone