Alcohol dehydrogenase from Entamoeba histolytica

===Alcohol Dehydrogenase from ''Entamoeba histolotica'' (EhADH1)===

<scene name='2oui/Tet/5'>Superposition</scene> of the structures of the <font color='lime'><b>wild-type apo-EhADH1 (alcohol dehydrogenase from ''Entamoeba histolotica'', colored lime</b></font>, [[1y9a]]) and the <font color='orange'><b>apo D275P-EhADH1 mutant (colored orange)</b></font> ([[2oui]]). <font color='red'><b>Pro275 and Asp275 are labeled red.</b></font> Residues within a distance of 4 Å from the mutation are shown (names of monomers are in brackets). Replacing <scene name='2oui/Tet/8'>Asp275</scene> with <scene name='2oui/Tet/7'>Pro</scene> significantly enhanced the thermal stability of EhADH1: ΔT_1/2^60min = +9.3°C, ΔT_1/2^CD = +10°C. The reverse mutation in the thermophilic alcohol dehydrogenase from ''Thermoanaerobacter brockii'' <scene name='Tetrameric_alcohol_dehydrogenases/Mut/3'>TbADH</scene> ([[1ykf]]; <font color='magenta'><b>colored magenta</b></font>) - substitution of wt TbADH Pro275 with <scene name='Tetrameric_alcohol_dehydrogenases/Mut/2'>Asp</scene> ([[2nvb]]; <font color='cyan'><b>colored cyan</b></font>) reduced the thermal stability of the enzyme: ΔT_1/2^60min = -13.8°C, ΔT_1/2^CD = -18.8°C. Nitrogen and oxygen atoms are colored in [http://en.wikipedia.org/wiki/CPK_coloring CPK colors]. <font color='red'><b>Pro275 and Asp275 are labeled red</b></font> (names of monomers are in brackets). These findings indicate that a single proline mutation is responsible for the significant differences in the thermal stability of ADHs, and show the importance of prolines in the protein stability. It was also shown that substitution by proline at the important positions could significantly stabilize the protein.