Sandbox Reserved 192: Difference between revisions

RNase A is made up of a single polypeptide chain of 124 residues. Of the 20 natural amino acids, RNase A possesses 19 of them, excluding tryptophan. This single polypeptide chain is cross-linked internally by four <scene name='Sandbox_Reserved_192/Disulfide_linkages/4'>disulfide linkages</scene>, which contribute to the stability of RNase A. Long four-stranded anti-parallel <scene name='Sandbox_Reserved_192/Beta_sheet/4'>ß-sheets</scene> and three short <scene name='Sandbox_Reserved_192/Alpha_helices/2'>α-helices</scene> make up the <scene name='Sandbox_Reserved_192/Secondary_structure/3'>secondary structure</scene> of RNase A. The structure of RNase A is often described as kidney shaped, with the active-site residues located within the cleft. <scene name='Sandbox_Reserved_192/Active_site/2'>Active site</scene> residues aid in catalysis. <scene name='Sandbox_Reserved_192/Lysine_41/3'>Lys41</scene> stabilizes the negative charge in the transition state, while <scene name='Sandbox_Reserved_192/His_12/3'>His12</scene> acts as a base and <scene name='Sandbox_Reserved_192/Histidine_119/2'>His119</scene> acts as an acid in catalysis. <scene name='Sandbox_Reserved_192/Catalytic_residues/2'>His12, Lys41, and His119</scene> are shown together here.    The amino acid sequence determines the three-dimensional structure of RNase A based on side-chain interactions.