Sandbox Reserved 1053: Difference between revisions
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== General Structure == | == General Structure == | ||
[[Image:Substrate Binding 2D Surface.jpg|200 px|left|thumb|Octylthioglucoside, a substrate analog, shown in the binding pocket of | [[Image:Substrate Binding 2D Surface.jpg|200 px|left|thumb|Octylthioglucoside, a substrate analog, shown in the binding pocket of [http://www.rcsb.org/pdb/explore/explore.do?structureId=1VA5 Ag85C]]] | ||
Antigen 85C was crystallized in its dimeric form.<ref>PMID: 25028518</ref> The <scene name='69/694220/Secondary_structures/2'>secondary structure</scene> shown in the monomeric form is composed of helices, shown in pink, with one interwoven beta sheet, shown in yellow. The confrontation of a central β-sheet bordered by α–helices creates an a α/β hydrolase fold in Ag85C, and this tertiary conformation is highly conserved across enzymes that function in this capacity. <ref>PMID:10655617</ref> The substrate binding pocket of Ag85C is composed of two separate but equally important components; there is carbohydrate binding pocket for the trehalose, and there is a fatty acid binding pocket for the mycolic acid. As a result, trehalose monomycolate can effectively bind to the Ag85C binding pocket. This binding pocket is shown in the left image with a substrate mimic. | Antigen 85C was crystallized in its dimeric form.<ref>PMID: 25028518</ref> The <scene name='69/694220/Secondary_structures/2'>secondary structure</scene> shown in the monomeric form is composed of helices, shown in pink, with one interwoven beta sheet, shown in yellow. The confrontation of a central β-sheet bordered by α–helices creates an a α/β hydrolase fold in Ag85C, and this tertiary conformation is highly conserved across enzymes that function in this capacity. <ref>PMID:10655617</ref> The substrate binding pocket of Ag85C is composed of two separate but equally important components; there is carbohydrate binding pocket for the trehalose, and there is a fatty acid binding pocket for the mycolic acid. As a result, trehalose monomycolate can effectively bind to the Ag85C binding pocket. This binding pocket is shown in the left image with a substrate mimic. | ||
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== Enzymatic Activity == | == Enzymatic Activity == | ||
[[Image:Substrate_Catalytic_Triad.jpg|300 px|right|thumb|Relation of the catalytic triad to the octylthioglucoside analog]] | [[Image:Substrate_Catalytic_Triad.jpg|300 px|right|thumb|Relation of the catalytic triad to the octylthioglucoside analog in [http://www.rcsb.org/pdb/explore/explore.do?structureId=1VA5 Ag85C]]] | ||
Mutagenesis studies have confirmed the Ag85C functions through a Glu-His-Ser <scene name='69/694220/Catalytic_triad/4'>catalytic triad</scene>, similar to that of [http://en.wikipedia.org/wiki/Chymotrypsin chymotrypsin]. By modifying each of the catalytic residues separately testing the enzyme’s relative activity, it has been shown that mutation of any one of these residues dramatically reduces activity. The S124 alcohol’s nucleophilicity is inductively strengthened through H260 and E224, which allows the S124 residue to catalyze a reaction that involves [http://en.wikipedia.org/wiki/Cord_factor trehalose 6, 6’-dimycolate]. The formation of the functional catalytic triad relies on upon Van der Waals interaction between C209 and the peptide bond between L232 and T231. This interaction results in a kinked conformation of the α9 helix, which promotes that activity of the catalytic triad. As a result, Ag85C, a mycolyl transferase, can facilitate the modification of trehalose monomycolates to trehalose dimycolates, which are then transported to the bacterial cell wall. This reaction is shown in the figure below. | Mutagenesis studies have confirmed the Ag85C functions through a Glu-His-Ser <scene name='69/694220/Catalytic_triad/4'>catalytic triad</scene>, similar to that of [http://en.wikipedia.org/wiki/Chymotrypsin chymotrypsin]. By modifying each of the catalytic residues separately testing the enzyme’s relative activity, it has been shown that mutation of any one of these residues dramatically reduces activity. The S124 alcohol’s nucleophilicity is inductively strengthened through H260 and E224, which allows the S124 residue to catalyze a reaction that involves [http://en.wikipedia.org/wiki/Cord_factor trehalose 6, 6’-dimycolate]. The formation of the functional catalytic triad relies on upon Van der Waals interaction between C209 and the peptide bond between L232 and T231. This interaction results in a kinked conformation of the α9 helix, which promotes that activity of the catalytic triad. As a result, Ag85C, a mycolyl transferase, can facilitate the modification of trehalose monomycolates to trehalose dimycolates, which are then transported to the bacterial cell wall. This reaction is shown in the figure below. | ||