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Isocitrate Lyase from Mycobacterium tuberculosis

1 Introduction
2 Protein Structure
3 Mechanism of Action
4 Disease Association
- 4.1 Clinical Implications
- 4.2 Ligand Bound

Introduction

TEXT TEXT TEXT

Protein Structure

Crystal Structure

Figure 2. Structure of Isocitrate Lyase. Quaternary structure is comprised of four subunits forming an alpha/beta barrel.

Isocitrate lyase (PDB Code 1F8I) is a tetramer with 222 symmetry. Each subunit is composed of 14 alpha helices and 14 beta sheets. A unique structural feature of this enzyme is a phenomenon called "". Helix swapping is observed between two monomers to form stable dimers. The 11th and 12th helices of each monomer exchange three dimensional placement with the respective helices of the opposite monomer. Due to the 222 symmetry observed, only two dimers form than combine to form the observed tetramer. As a result of this structure, 18% of the surface of each monomer is buried within the protein.

Active Site Residues

Inhibitors

Mechanism of Action

Image:TCA Cycle.png

Figure 1. Citric Acid Cycle with Glyoxylate Shunt Pathway. In several bacterial species, there is a carbon conserving gloxylate shunt pathway that converts isocitrate to malate in two steps instead of the usual five steps.

Disease Association

Clinical Implications

Mycobacterium tuberculosis is a respiratory infection that causes numerous fatalities throughout the world. It lives in organisms and feeds off of host cells, which indicate a variety of lipases exist within M. tuberculosis. Current drugs that are on the market now target a small number of bacterial processes like cell wall formation and chromosomal replication. Although several antibiotics exist, all of them target these same mechanisms of inhibition. These commonalities have led to the prevalence of different multi-drug resistant (MDR) tuberculosis strains. Due to the high level of resistance, finding a lasting treatment for MDR TB infections has become very problematic. Studies into new mechanisms of inhibition will be crucial to prevent widespread outbreaks. Isocitrate lyase plays a key role in survival of M. tuberculosis by sustaining intracellular infections in inflammatory respiratory macrophages. Used in the citric acid cycle, isocitrate lyase is the first enzyme catalyzing the carbon conserving glyoxylate pathway. This glyoxylate pathway has not been observed in mammals and thus presents a unique drug target to solely attack TB infections.

Ligand Bound

Figure 3. Active site residues hydrogen bound to a cofactor and the products of the catalyzed isocitrate reaction. Glyoxylate is shown in blue, succinate is shown in green, and the Mg²⁺ cofactor is shown in yellow.

References

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@@ Line 1: / Line 1: @@
 =='''Isocitrate Lyase from ''Mycobacterium tuberculosis'''''==
 <StructureSection load='1F8I' size='340' side='right' caption='Isocitrate Lyase' scene='>
-==Relevance==
+==Introduction==
-===Background===
+TEXT TEXT TEXT
-''Mycobacterium tuberculosis'' is a respiratory infection that causes numerous fatalities throughout the world. It lives in organisms and feeds off of host cells, which indicate a variety of lipases exist within ''M. tuberculosis''. Current drugs that are on the market now target a small number of bacterial processes like cell wall formation and chromosomal replication. Although several antibiotics exist, all of them target these same mechanisms of inhibition. These commonalities have led to the prevalence of different multi-drug resistant (MDR) tuberculosis strains. Due to the high level of resistance, finding a lasting treatment for MDR TB infections has become very problematic. Studies into new mechanisms of inhibition will be crucial to prevent widespread outbreaks.
-===Clinical Implications===
-Isocitrate lyase plays a key role in survival of ''M. tuberculosis'' by sustaining intracellular infections in inflammatory respiratory macrophages. Used in the citric acid cycle, isocitrate lyase is the first enzyme catalyzing the carbon conserving glyoxylate pathway. This glyoxylate pathway has not been observed in mammals and thus presents a unique drug target to solely attack TB infections.
-===Mechanism of Action===
-[[Image:TCA_Cycle.png|500 px|left|thumb|'''Figure 1. Citric Acid Cycle with Glyoxylate Shunt Pathway.''' In several bacterial species, there is a carbon conserving gloxylate shunt pathway that converts isocitrate to malate in two steps instead of the usual five steps.]]
 ==Protein Structure==
@@ Line 15: / Line 10: @@
 Helix swapping is observed between two monomers to form stable dimers. The 11th and 12th helices of each monomer exchange three dimensional placement with the respective helices of the opposite monomer. Due to the 222 symmetry observed, only two dimers form than combine to form the observed tetramer. As a result of this structure, 18% of the surface of each monomer is buried within the protein.
-===Ligand Bound===
+===Active Site Residues===
-[[Image:Active_Site_Hydrogen_Bonding.png|250 px|center|thumb|'''Figure 3. Active site residues hydrogen bound to a cofactor and the products of the catalyzed isocitrate reaction.''' Glyoxylate is shown in blue, succinate is shown in green, and the Mg<sup>2+</sup> cofactor is shown in yellow.]]
-== Function ==
-== Structural highlights ==
+===Inhibitors===
-This is a sample scene created with SAT to <scene name="/12/3456/Sample/1">color</scene> by Group, and another to make <scene name="/12/3456/Sample/2">a transparent representation</scene> of the protein. You can make your own scenes on SAT starting from scratch or loading and editing one of these sample scenes.
+==Mechanism of Action==
+[[Image:TCA_Cycle.png|500 px|left|thumb|'''Figure 1. Citric Acid Cycle with Glyoxylate Shunt Pathway.''' In several bacterial species, there is a carbon conserving gloxylate shunt pathway that converts isocitrate to malate in two steps instead of the usual five steps.]]
+==Disease Association==
+===Clinical Implications===
+''Mycobacterium tuberculosis'' is a respiratory infection that causes numerous fatalities throughout the world. It lives in organisms and feeds off of host cells, which indicate a variety of lipases exist within ''M. tuberculosis''. Current drugs that are on the market now target a small number of bacterial processes like cell wall formation and chromosomal replication. Although several antibiotics exist, all of them target these same mechanisms of inhibition. These commonalities have led to the prevalence of different multi-drug resistant (MDR) tuberculosis strains. Due to the high level of resistance, finding a lasting treatment for MDR TB infections has become very problematic. Studies into new mechanisms of inhibition will be crucial to prevent widespread outbreaks.
+Isocitrate lyase plays a key role in survival of ''M. tuberculosis'' by sustaining intracellular infections in inflammatory respiratory macrophages. Used in the citric acid cycle, isocitrate lyase is the first enzyme catalyzing the carbon conserving glyoxylate pathway. This glyoxylate pathway has not been observed in mammals and thus presents a unique drug target to solely attack TB infections.
+===Ligand Bound===
+[[Image:Active_Site_Hydrogen_Bonding.png|250 px|center|thumb|'''Figure 3. Active site residues hydrogen bound to a cofactor and the products of the catalyzed isocitrate reaction.''' Glyoxylate is shown in blue, succinate is shown in green, and the Mg<sup>2+</sup> cofactor is shown in yellow.]]
 </StructureSection>
 == References ==