<p>This entry represents a repeat of about 40 amino acids found in a variety of archaea and bacteria which can be present in up to 14 copies per protein. The archaeal species <taxon tax_id="2209">Methanosarcina mazei</taxon> (Methanosarcina frisia) contains several predicted surface layer proteins (SLPs) containing tandem copies of this repeat [<cite idref="PUB00014157"/>]. The crystal structure of one of these proteins (<db_xref db="SWISSPROT" dbkey="Q50245"/>), containing seven tandem copies of this repeat, was examined. Individually, these repeats form four-stranded beta blades, while the seven copies together form a seven-bladed beta propeller domain. This repeat shows sequence similarity to the WD-40 repeat (<db_xref db="INTERPRO" dbkey="IPR001680"/>) and may play a similar role, serving as a rigid scaffold for protein interactions.</p> YVTN beta-propeller repeat