 However the alpha strand conformation is observed in isolated instances in native state proteins as solved by X-ray crystallography or protein NMR, although an extended alpha sheet is not identified in any known natural protein.Native proteins containing alpha-strand regions or alpha-sheet-patterned hydrogen bonding include synaptotagmin, lysozyme, and potassium channels, where the alpha-strands line the ion-conducting pore.Evidence for the existence of alpha-sheet in a mutant form of transthyretin has been presented.