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User:Michael Roberts/BIOL115 Chymo: Difference between revisions

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Click on the ''' 'green links' ''' in the text in the scrollable section below to examine this molecule in more detail.
Click on the ''' 'green links' ''' in the text in the scrollable section below to examine this molecule in more detail.


<StructureSection load='1afq' size='700' side='right' caption='Structure of bovine chymotrypsin (PDB entry [[1afq]])' scene='User:Michael_Roberts/BIOL115_Chymo/Start/1'>
<StructureSection load='1afq' size='600' side='right' caption='Structure of bovine chymotrypsin (PDB entry [[1afq]])' scene='User:Michael_Roberts/BIOL115_Chymo/Start/1'>
== Tertiary structure ==
== Tertiary structure ==
Chymotrypsin is initially synthesized as a 245 amino acid inactive precursor (a zymogen) termed chymotrypsinogen. Activation of chymotrypsinogen involves proteolytic cleavage at two sites along the chain and removal of two amino acids at each cleavage site. The resultant <scene name='User:Michael_Roberts/BIOL115_Chymo/Chains/1'>three chains</scene> are shown here (chain 1 = 1-13 in green; chain 2 = 16-146 in red; chain 3 = 149-24 in blue). Note, some amino acids at the temini of these chains are not shown in this representation (e.g. 11-13, 149, ). This is because these residues show too much flexibility in the crystal structures to give  X-ray diffraction patterns which would locate them in space.
Chymotrypsin is initially synthesized as a 245 amino acid inactive precursor (a zymogen) termed chymotrypsinogen. Activation of chymotrypsinogen involves proteolytic cleavage at two sites along the chain and removal of two amino acids at each cleavage site. The resultant <scene name='User:Michael_Roberts/BIOL115_Chymo/Chains/1'>three chains</scene> are shown here (chain 1 = 1-13 in green; chain 2 = 16-146 in red; chain 3 = 149-24 in blue). Note, some amino acids at the temini of these chains are not shown in this representation (e.g. 11-13, 149, ). This is because these residues show too much flexibility in the crystal structures to give  X-ray diffraction patterns which would locate them in space.
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== Beta Barrels, Protein Domains and the Active Center ==
== 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 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.


''Colour key:''
''Colour key:''
{{Template:ColorKey_Helix}},
{{Template:ColorKey_Helix}},
{{Template:ColorKey_Strand}}.
{{Template:ColorKey_Strand}}.
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.




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