User:Michael Roberts/BIOL115 Chymo: Difference between revisions

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The three chains are held together by five <scene name='User:Michael_Roberts/BIOL115_Chymo/Chains/2'>disulfide bonds</scene>. Can you identify the specific cys residues linked in each disulfide bond? Why do you think is it very difficult to obtain active chymotrypsin after denaturation and renaturation?

== Beta Barrels, Protein Domains and the Active Center ==

The chymotrypsin molecule is folded into two <scene name='User:Michael_Roberts/BIOL115_Chymo/2ndry_structure/1'>domains</scene>, each containing six beta strands (orange) arranged as anti-parallel sheets which form a circular structure known as a beta barrel. Rotate the molecule so that you can see down through each of the two beta barrels in turn.

The <scene name='User:Michael_Roberts/BIOL115_Chymo/2ndry_structure/2'>active site residues</scene> (Ser-195, His-57 and Asp-102 shown here in spacefill representation), are far apart in the primary sequence but are brought together in a crevice formed between the two beta barrel protein domains.

== The Active Site Triad ==

The <scene name='User:Michael_Roberts/BIOL115_Chymo/2ndry_structure/3'>active site</scene> of chymotrypsin consists of Asp102 positioned close to His 57 and Ser 195. The precise mechanism of action is still debated, but it appears that a hydrogen on the his imidazole ring is transferred to the Asp 102 carboxylate (either via a "charge relay system" or via a "low barrier H-bond"). This shift results in the histidine ring being able to accept the serine 195 hydroxyl hydrogen, forming a very nucleophilic serine alkoxide ion.

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 The three chains are held together by five <scene name='User:Michael_Roberts/BIOL115_Chymo/Chains/2'>disulfide bonds</scene>. Can you identify the specific cys residues linked in each disulfide bond? Why do you think is it very difficult  to obtain active chymotrypsin after denaturation and renaturation?
+== Beta Barrels, Protein Domains and the Active Center ==
+The chymotrypsin molecule is folded into two <scene name='User:Michael_Roberts/BIOL115_Chymo/2ndry_structure/1'>domains</scene>, each containing six beta strands (orange) arranged as anti-parallel sheets which form a circular structure known as a beta barrel. Rotate the molecule so that you can see down through each of the two beta barrels in turn.
+The <scene name='User:Michael_Roberts/BIOL115_Chymo/2ndry_structure/2'>active site residues</scene> (Ser-195, His-57 and Asp-102 shown here in spacefill representation), are far apart in the primary sequence but are brought together in a crevice formed between the two beta barrel protein domains.
+== The Active Site Triad ==
+The <scene name='User:Michael_Roberts/BIOL115_Chymo/2ndry_structure/3'>active site</scene> of chymotrypsin consists of Asp102 positioned close to His 57 and Ser 195. The precise mechanism of action is still debated, but it appears that a hydrogen on the his imidazole ring is transferred to the Asp 102 carboxylate (either via a "charge relay system" or via a "low barrier H-bond"). This shift results in the histidine ring being able to accept the serine 195 hydroxyl hydrogen, forming a very nucleophilic serine alkoxide ion.