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User:Amy Kerzmann/Sandbox 5
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The <scene name='User:Amy_Kerzmann/Sandbox_5/New_trypsin-wt-triad/6' target='1'>trypsin binding pocket</scene> contains <font color="FF0000">Asp189</font> to select for positively charged sidechains. Where is the <scene name='User:Amy_Kerzmann/Sandbox_5/New_trypsin-wt-triad/7' target='1'>trypsin disulfide bond</scene> in this structure? | The <scene name='User:Amy_Kerzmann/Sandbox_5/New_trypsin-wt-triad/6' target='1'>trypsin binding pocket</scene> contains <font color="FF0000">Asp189</font> to select for positively charged sidechains. Where is the <scene name='User:Amy_Kerzmann/Sandbox_5/New_trypsin-wt-triad/7' target='1'>trypsin disulfide bond</scene> in this structure? | ||
| - | The <scene name='User:Amy_Kerzmann/Sandbox_5/New_elastase-triad/ | + | The <scene name='User:Amy_Kerzmann/Sandbox_5/New_elastase-triad/6' target='2'>elastase binding pocket</scene> is more constrained, explaining the preference for smaller residues. Based on the other two structures, would you predict the presence of an <scene name='User:Amy_Kerzmann/Sandbox_5/New_elastase-triad/7' target='2'>elastase disulfide bond</scene>? |
Revision as of 18:44, 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 .
As we have just seen, these three serine proteases have relatively similar active sites. What then accounts for their varying specificities? To answer this question, the next links examine the binding pockets of each protein. The spacefilled residues have been color coded according to hydrophobicity.
The is large, deep and relatively hydrophobic. This structure accommodates bulky aromatic and aliphatic sidechains. Also note the presence of a between Cys191 and Cys220. What role might this covalent bond have in the protein's function?
The contains Asp189 to select for positively charged sidechains. Where is the in this structure?
The is more constrained, explaining the preference for smaller residues. Based on the other two structures, would you predict the presence of an ?
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.
