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User:Amy Kerzmann/Sandbox 5
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Now compare chymotrypsin to <scene name='User:Amy_Kerzmann/Sandbox_5/New_trypsin-wt-triad/3' target='1'>trypsin catalytic triad</scene>. The <scene name='User:Amy_Kerzmann/Sandbox_5/New_elastase-triad/2' target='2'>elastase catalytic triad</scene>. | Now compare chymotrypsin to <scene name='User:Amy_Kerzmann/Sandbox_5/New_trypsin-wt-triad/3' target='1'>trypsin catalytic triad</scene>. The <scene name='User:Amy_Kerzmann/Sandbox_5/New_elastase-triad/2' target='2'>elastase catalytic triad</scene>. | ||
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| + | The <scene name='User:Amy_Kerzmann/Sandbox_5/New_chymotrypsin-triad/4'>chymotrypsin binding pocket</scene> is large, deep and relatively hydrophobic. This structure accommodates bulky aromatic and aliphatic sidechains. | ||
The <scene name='User:Amy_Kerzmann/Sandbox_5/New_trypsin-wt-triad/2' target='1'>trypsin binding pocket</scene> contains <font color="FF0000">Asp189</font> to select for positively charged sidechains. | The <scene name='User:Amy_Kerzmann/Sandbox_5/New_trypsin-wt-triad/2' target='1'>trypsin binding pocket</scene> contains <font color="FF0000">Asp189</font> to select for positively charged sidechains. | ||
Revision as of 18:14, 10 February 2010
Serine Proteases
The most famous members of the serine protease family are trypsin, chymotrypsin and elastase. These digestive enzymes are also useful tools in biochemistry and molecular biology to ascertain protein sequences.
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From the structures above, it is apparent that these three enzymes have similar folds. There are also extensive similarities, or conservation, at the level of primary structure. However, there are small changes among the proteins, which is why they have similar function, but remarkably different specificities. Therefore, serine proteases area classic example of how STRUCTURE dictates FUNCTION!
Serine proteases perform their catalytic roles using three key residues: Ser, His, Asp. Because the proteases utilize these three residues for function, they are referred to as the catalytic triad. Highlight the . Click on the structure image to determine the residue numbers for Ser, Asp and His. (Hint: a code will appear in the lower left-hand corner of the browser window.)
Now compare chymotrypsin to . The .
The is large, deep and relatively hydrophobic. This structure accommodates bulky aromatic and aliphatic sidechains.
The contains Asp189 to select for positively charged sidechains.
The contains Gly190, Val216 and Thr226.
By highlighting the solvent-accessible surfaces of and , one can better understand why trypsin has specificity for large, charged sidechains whereas elastase targets smaller residues.
