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by Kelly Hrywkiw
by Kelly Hrywkiw
{{STRUCTURE_2h9i |  PDB=2h9i  |  SCENE=  }}
{{STRUCTURE_2h9i |  PDB=2h9i  |  SCENE=  }}
[[Image:Secondary Structure of inhA.png|thumb|left|Width200Height300|alt=Secondary Structure Succession of inhA. Secondary structure residues are ordered from blue to red.|Secondary structure succession inhA.]]
__TOC__
__TOC__
[[Image:Secondary Structure of inhA.png|thumb|left|Width200Height300|alt=Secondary Structure Succession of inhA. Secondary structure residues are ordered from blue to red.|Secondary structure succession inhA.]]


=Introduction=
=Introduction=


The enzyme inhA is coded from the inhA gene that is simillar in sequence to the ''[http://en.wikipedia.org/wiki/Salmonella_typhimurium Salmonella typhimurium]''gene which plays a role in fatty acid biosynthesis <ref name ="making drugs for inhA">Sacchettini, James (New Rochelle, NY) 1999 INHA crystals and three dimensional structure United States Albert Einstein College of Medicine of Yeshiva University (Bronx, NY) 5882878 http://www.freepatentsonline.com/5882878.html</ref>. Inha is an NADH dependent trans enoyl-acyl ACP carrier protein that plays a role in the sysnthesis of [http://en.wikipedia.org/wiki/Mycolic_acid Mycolic Acid], and is part of a short-chain dehydrogenase/reductase family <ref name ="mech of thioamide drug action">PMID:17227913</ref><ref name ="phosphorylation of inhA">PMID:21143326</ref>.  Mycolic acids are long chain fatty acids that are essential in cell wall formation of the human pathogen ''[http://en.wikipedia.org/wiki/Mycobacterium_tuberculosis Mycobacterium tuberculosis]''as well as other mycobateria such as ''[http://en.wikipedia.org/wiki/Mycobacterium_leprae Mycobacterium leprae]''<ref name ="TB">PMID2568869:</ref>. Inha has been propsed as the target of the thionamide drugs, ethionamide (ETH)  and isoniazid (INH), which have been used in treatment of mycobacterial infections <ref name ="phosphorylation of inhA">PMID:21143326</ref>.   
The enzyme inhA is coded from the inhA gene that is simillar in sequence to the ''[http://en.wikipedia.org/wiki/Salmonella_typhimurium Salmonella typhimurium]''gene which plays a role in fatty acid biosynthesis <ref name ="making drugs for inhA">Sacchettini, James (New Rochelle, NY) 1999 INHA crystals and three dimensional structure United States Albert Einstein College of Medicine of Yeshiva University (Bronx, NY) 5882878 http://www.freepatentsonline.com/5882878.html</ref>. Inha is an NADH dependent trans enoyl-acyl ACP carrier protein that plays a role in the sysnthesis of [http://en.wikipedia.org/wiki/Mycolic_acid Mycolic Acid], and is part of a short-chain dehydrogenase/reductase family <ref name ="mech of thioamide drug action">PMID:17227913</ref><ref name ="phosphorylation of inhA">PMID:21143326</ref>.  Mycolic acids are long chain fatty acids that are essential in cell wall formation of the human pathogen ''[http://en.wikipedia.org/wiki/Mycobacterium_tuberculosis Mycobacterium tuberculosis]''as well as other mycobateria such as ''[http://en.wikipedia.org/wiki/Mycobacterium_leprae Mycobacterium leprae]''<ref name ="TB">PMID2568869:</ref>. Inha has been propsed as the target of the [http://en.wikipedia.org/wiki/Thioamidedrugs thioamide] drugs, ethionamide (ETH)  and isoniazid (INH), which have been used in treatment of mycobacterial infections <ref name ="phosphorylation of inhA">PMID:21143326</ref>.   




=Structure of inhA=
=Structure of inhA=


<Structure load='2h9i' size='300' frame='true' align='left' caption='Momomeric subunit of inhA' scene='Sandbox_Reserved_321/Structural_progresion/1' />
The inhA enzyme of ''M. tuberculosis'' is a homotetramer composed of a repeating subunit comprised of a single domain with a [http://en.wikipedia.org/wiki/Rossmann_fold Rossmann Fold] in the core that provides a NADH binding site<ref name ="crystallographic studies"/>.  The single domain can be broken down into two substructures that are connected by short peptide loop<ref name ="making drugs for inhA"/><ref name ="crystallographic studies">PMID:17588773</ref>. 
 
<Structure load='2h9i' size='250' frame='true' align='left' caption='Momomeric subunit of inhA' scene='Sandbox_Reserved_321/Structural_progresion/1' />


The inhA enzyme of ''[http://en.wikipedia.org/wiki/Mycobacterium_tuberculosis Mycobacterium tuberculosis]'' is a homotetramer composed of a repeating subunit comprised of a single domain with a [http://en.wikipedia.org/wiki/Rossmann_fold Rossmann Fold] in the core that provides a NADH binding site<ref name ="crystallographic studies"/>.  The single domain can be broken down into two substructures that are connected by short peptide loop<ref name ="making drugs for inhA"/><ref name ="crystallographic studies">PMID:17588773</ref>. 


==Substructure 1 of inhA==
==Substructure 1 of inhA==
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The first substructure can be further broken down into two sections, the <scene name='Sandbox_Reserved_321/Substructure1section1/7'>first section</scene> consisting of two β strands <scene name='Sandbox_Reserved_321/B-1_and_b-2/4'>(B-1 and B-2)</scene>and two short α helicies <scene name='Sandbox_Reserved_321/A-1_and_a-2/2'>(A-1 and A-2)</scene><ref name ="making drugs for inhA"/>.   
The first substructure can be further broken down into two sections, the <scene name='Sandbox_Reserved_321/Substructure1section1/7'>first section</scene> consisting of two β strands <scene name='Sandbox_Reserved_321/B-1_and_b-2/4'>(B-1 and B-2)</scene>and two short α helicies <scene name='Sandbox_Reserved_321/A-1_and_a-2/2'>(A-1 and A-2)</scene><ref name ="making drugs for inhA"/>.   
The first section is connected to the <scene name='Sandbox_Reserved_321/Section2substructure1/1'>second section</scene> by a β strand <scene name='Sandbox_Reserved_321/B-3/1'>(B-3)</scene> that crosses over the two domains, and leads into the second section initiating at the third α helix <scene name='Sandbox_Reserved_321/A-3/1'>(A-3)</scene><ref name ="making drugs for inhA"/>(A-3) is connected by a long loop to a 14 residue β strand <scene name='Sandbox_Reserved_321/B-4/2'>(B-4)</scene>that then leads into the fourth α helix <scene name='Sandbox_Reserved_321/A-4/2'>(A-4)</scene><ref name ="making drugs for inhA"/>. A-4 then leads into a fifth strand β <scene name='Sandbox_Reserved_321/B-5/1'>(B-5)</scene>, followed by a 25 residue α helix <scene name='Sandbox_Reserved_321/A-5/2'>(A-5)</scene>, and into the final strand β <scene name='Sandbox_Reserved_321/B-6/1'>(B-6)</scene><ref name ="making drugs for inhA"/>.   
The first section is connected to the <scene name='Sandbox_Reserved_321/Section2substructure1/1'>second section</scene> by a β strand <scene name='Sandbox_Reserved_321/B-3/1'>(B-3)</scene> that crosses over the two domains, and leads into the second section initiating at the third α helix <scene name='Sandbox_Reserved_321/A-3/1'>(A-3)</scene><ref name ="making drugs for inhA"/>(A-3) is connected by a long loop to a 14 residue β strand <scene name='Sandbox_Reserved_321/B-4/2'>(B-4)</scene>that then leads into the fourth α helix <scene name='Sandbox_Reserved_321/A-4/2'>(A-4)</scene><ref name ="making drugs for inhA"/>. A-4 then leads into a fifth strand β <scene name='Sandbox_Reserved_321/B-5/1'>(B-5)</scene>, followed by a 25 residue α helix <scene name='Sandbox_Reserved_321/A-5/2'>(A-5)</scene>, and into the final strand β <scene name='Sandbox_Reserved_321/B-6/1'>(B-6)</scene><ref name ="making drugs for inhA"/>.   


==Substructure 2 of inhA==
==Substructure 2 of inhA==
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<scene name='Sandbox_Reserved_321/Substructure_2/1'>Substructure 2</scene> contains the c-terminal region of the molecule and consists of a small β strand <scene name='Sandbox_Reserved_321/B-7/1'>(B-7)</scene>, and two α helicies <scene name='Sandbox_Reserved_321/A-6_and_a-7/1'>(A-6 and A-7)</scene> which are conected by a short five residue loop<ref name ="making drugs for inhA"/>.  The C-terminal domain consits of two other α helicies <scene name='Sandbox_Reserved_321/A-8_and_a-9/1'>(A-8 and A-9)</scene><ref name ="making drugs for inhA"/>.
<scene name='Sandbox_Reserved_321/Substructure_2/1'>Substructure 2</scene> contains the c-terminal region of the molecule and consists of a small β strand <scene name='Sandbox_Reserved_321/B-7/1'>(B-7)</scene>, and two α helicies <scene name='Sandbox_Reserved_321/A-6_and_a-7/1'>(A-6 and A-7)</scene> which are conected by a short five residue loop<ref name ="making drugs for inhA"/>.  The C-terminal domain consits of two other α helicies <scene name='Sandbox_Reserved_321/A-8_and_a-9/1'>(A-8 and A-9)</scene><ref name ="making drugs for inhA"/>.


=Physiological Function=
 
 
 
 
 
 
=Function=
 
InhA plays a key role in the synthesis of fatty acids, particularly in ''M. tuberculosis'' which has type one fatty acid synthesis (FASI) and type two fatty acid synthesis (FASII) which together funtion in the synthesis of mycolic acids.<ref name ="Function of M Tb">PMID:18552191</ref>.  The final step in FASII is compleated by InhA which reduces 2-trans-enoyl-ACP's with chain lengths over twelve carbons <ref name ="Function of M Tb"/>


=Role in the Mycolic Acid Pathway=
=Role in the Mycolic Acid Pathway=


[[Image:Pathway.png|thumb|right|upright=2|alt=Proposed mechanism.|Formulated mechanism of Mycolic acid synthesis as proposed by  Wilson et al.<ref name ="Drug Induced Alterations">10536008 </ref>.]]   
[[Image:Pathway.png|thumb|right|upright=2|alt=Proposed mechanism.|Formulated mechanism of Mycolic acid synthesis as proposed by  Wilson et al.<ref name ="Drug Induced Alterations">PMID:10536008</ref>.]]   




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=References=
=References=
<references/>

Revision as of 01:02, 1 April 2011

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InhA

by Kelly Hrywkiw

Drag the structure with the mouse to rotate
2h9i, resolution 2.20Å (default scene)
Ligands: EAD
Gene: inhA (Mycobacterium tuberculosis)
Activity: [acyl-carrier-protein_reductase_(NADH) Enoyl-[acyl-carrier-protein] reductase (NADH)], with EC number 1.3.1.9
Related: 1zid
Resources: FirstGlance, OCA, PDBsum, RCSB
Coordinates: save as pdb, mmCIF, xml


Secondary Structure Succession of inhA. Secondary structure residues are ordered from blue to red.
Secondary structure succession inhA.

Introduction

The enzyme inhA is coded from the inhA gene that is simillar in sequence to the Salmonella typhimuriumgene which plays a role in fatty acid biosynthesis [1]. Inha is an NADH dependent trans enoyl-acyl ACP carrier protein that plays a role in the sysnthesis of Mycolic Acid, and is part of a short-chain dehydrogenase/reductase family [2][3]. Mycolic acids are long chain fatty acids that are essential in cell wall formation of the human pathogen Mycobacterium tuberculosisas well as other mycobateria such as Mycobacterium leprae[4]. Inha has been propsed as the target of the thioamide drugs, ethionamide (ETH) and isoniazid (INH), which have been used in treatment of mycobacterial infections [3].


Structure of inhA

The inhA enzyme of M. tuberculosis is a homotetramer composed of a repeating subunit comprised of a single domain with a Rossmann Fold in the core that provides a NADH binding site[5]. The single domain can be broken down into two substructures that are connected by short peptide loop[1][5].

Momomeric subunit of inhA

Drag the structure with the mouse to rotate


Substructure 1 of inhA

Substructure 1 consists of 6 parallel β strands and 4 α helices interwoven together to form a core α/β structure that contains the n-terminal domain[1]. The first substructure can be further broken down into two sections, the first section consisting of two β strands (B-1 and B-2)and two short α helicies (A-1 and A-2)[1]. The first section is connected to the second section by a β strand (B-3) that crosses over the two domains, and leads into the second section initiating at the third α helix (A-3)[1](A-3) is connected by a long loop to a 14 residue β strand (B-4)that then leads into the fourth α helix (A-4)[1]. A-4 then leads into a fifth strand β (B-5), followed by a 25 residue α helix (A-5), and into the final strand β (B-6)[1].


Substructure 2 of inhA

Substructure 2 contains the c-terminal region of the molecule and consists of a small β strand (B-7), and two α helicies (A-6 and A-7) which are conected by a short five residue loop[1]. The C-terminal domain consits of two other α helicies (A-8 and A-9)[1].




Function

InhA plays a key role in the synthesis of fatty acids, particularly in M. tuberculosis which has type one fatty acid synthesis (FASI) and type two fatty acid synthesis (FASII) which together funtion in the synthesis of mycolic acids.[6]. The final step in FASII is compleated by InhA which reduces 2-trans-enoyl-ACP's with chain lengths over twelve carbons [6]

Role in the Mycolic Acid Pathway

Proposed mechanism.
Formulated mechanism of Mycolic acid synthesis as proposed by Wilson et al.[7].


Protein Superfamilly

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Sacchettini, James (New Rochelle, NY) 1999 INHA crystals and three dimensional structure United States Albert Einstein College of Medicine of Yeshiva University (Bronx, NY) 5882878 https://www.freepatentsonline.com/5882878.html
  2. ↑ Wang F, Langley R, Gulten G, Dover LG, Besra GS, Jacobs WR Jr, Sacchettini JC. Mechanism of thioamide drug action against tuberculosis and leprosy. J Exp Med. 2007 Jan 22;204(1):73-8. Epub 2007 Jan 16. PMID:17227913 doi:10.1084/jem.20062100
  3. ↑ 3.0 3.1 Molle V, Gulten G, Vilcheze C, Veyron-Churlet R, Zanella-Cleon I, Sacchettini JC, Jacobs WR Jr, Kremer L. Phosphorylation of InhA inhibits mycolic acid biosynthesis and growth of Mycobacterium tuberculosis. Mol Microbiol. 2010 Dec;78(6):1591-605. doi:, 10.1111/j.1365-2958.2010.07446.x. Epub 2010 Nov 9. PMID:21143326 doi:10.1111/j.1365-2958.2010.07446.x
  4. ↑ PMID2568869:
  5. ↑ 5.0 5.1 Dias MV, Vasconcelos IB, Prado AM, Fadel V, Basso LA, de Azevedo WF Jr, Santos DS. Crystallographic studies on the binding of isonicotinyl-NAD adduct to wild-type and isoniazid resistant 2-trans-enoyl-ACP (CoA) reductase from Mycobacterium tuberculosis. J Struct Biol. 2007 Sep;159(3):369-80. Epub 2007 May 3. PMID:17588773 doi:https://dx.doi.org/10.1016/j.jsb.2007.04.009
  6. ↑ 6.0 6.1 Gurvitz A, Hiltunen JK, Kastaniotis AJ. Function of heterologous Mycobacterium tuberculosis InhA, a type 2 fatty acid synthase enzyme involved in extending C20 fatty acids to C60-to-C90 mycolic acids, during de novo lipoic acid synthesis in Saccharomyces cerevisiae. Appl Environ Microbiol. 2008 Aug;74(16):5078-85. Epub 2008 Jun 13. PMID:18552191 doi:10.1128/AEM.00655-08
  7. ↑ Wilson M, DeRisi J, Kristensen HH, Imboden P, Rane S, Brown PO, Schoolnik GK. Exploring drug-induced alterations in gene expression in Mycobacterium tuberculosis by microarray hybridization. Proc Natl Acad Sci U S A. 1999 Oct 26;96(22):12833-8. PMID:10536008
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