TIM barrel

In molecular biology the TIM barrel is a conserved protein fold consisting of eight a-helices and eight parallel ß-strands that alternate along the peptide backbone. The structure is named after triosephosphate isomerase, a conserved metabolic enzyme. TIM barrels are one of the most common protein folds. One of the most intriguing features among members of this class of proteins is although they all exhibit the same tertiary fold there is very little sequence similarity between them. At least 15 distinct enzyme families use this framework to generate the appropriate active site geometry, always at the C-terminal end of the eight parallel beta-strands of the barrel.