Triosephosphate Isomerase: Difference between revisions

The enzyme is a dimer of identical subunits. The tertiary fold of each subunit is an alpha/beta barrel of which TIM is the prototype.(<scene name='Triosephosphate_Isomerase/Timscene1test/3'>alpha/beta barrel structure</scene>) Eight parallel beta strands (purple) form the wall of the barrel, which is located in the protein’s interior. Alpha helices (blue), which are connected to the beta strands, form the outer rim of the enzyme. Regions between the alpha helices and beta strands are also shown (green). The curvature of the barrel arises principally from the right-handed twist of the beta sheet. Nonpolar amino acids pointing inward from the beta strands contribute to the hydrophobic (<scene name='Triosephosphate_Isomerase/Tim_hydro_polar/3'>hydrophobicity</scene>) core of the structure (grey), whereas residues pointing outward interact with the nonpolar face of the alpha helices on the outer rim (fuchsia).  The active site is found at the carboxyl end of the barrel structure. Key active site residues include Glu165 (yellow), His95 (green), and Lys12 (blue). A flexible loop of residues 168 – 177 (highlighted in red) functions as a lid to the active site.  It opens to provide access of the substrate to the active site, and it closes the active site upon substrate binding.<scene name='Triosephosphate_Isomerase/Tim_activesite1/1'>active site</scene>