English: Ribbon schematic of a 3-sided, lefthanded beta-helix protein subunit (end view). Beta strands are shown as arrows; the backbone spirals clockwise up toward the viewer in the neatly triangular parallel beta sheets. The final turn (orange) is protected from possible aggregation by the small alpha-heix that lies across it. From the 1QRE archaeal carbonic anhydrase structure, visualized in Mage and rendered by Raster3D.