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Sandbox GGC4

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== Function ==
== Function ==
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Lipoate Protein Ligase A is a monomeric protein in ''e. coli'' that catalyzes the reaction to add lipoic acid to other enzymes that require it. <ref>PMID:7639702</ref> This is a two step reaction. First, ATP is cleaved into AMP and pyrophosphate, and AMP is then attached to lipoate molecule. Then, Lipoate Protein Ligase attaches the lipoic acid to a desired protein; the AMP is removed from lipoate in this process. The lipoate is typically taken up by specific lysine residues in the receiving protein, and used as a prosthetic group.
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Lipoate Protein Ligase A is a monomeric protein in ''e. coli'' that catalyzes the reaction to add lipoic acid to other enzymes that require it. <ref>PMID:7639702</ref> This is a two step reaction. First, ATP is cleaved into AMP and pyrophosphate, and AMP is then attached to lipoate molecule. <ref>PMID:16043486</ref> Then, Lipoate Protein Ligase attaches the lipoic acid to a desired protein; the AMP is removed from lipoate in this process. <ref>PMID:16043486</ref> The lipoate is typically taken up by specific lysine residues in the receiving protein, and used as a prosthetic group.
== Disease ==
== Disease ==

Revision as of 09:42, 21 April 2018

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This is a default text for your page Sandbox GGC4. Click above on edit this page to modify. Be careful with the < and > signs. You may include any references to papers as in: the use of JSmol in Proteopedia [1] or to the article describing Jmol [2] to the rescue.

Contents

Function

Lipoate Protein Ligase A is a monomeric protein in e. coli that catalyzes the reaction to add lipoic acid to other enzymes that require it. [3] This is a two step reaction. First, ATP is cleaved into AMP and pyrophosphate, and AMP is then attached to lipoate molecule. [4] Then, Lipoate Protein Ligase attaches the lipoic acid to a desired protein; the AMP is removed from lipoate in this process. [5] The lipoate is typically taken up by specific lysine residues in the receiving protein, and used as a prosthetic group.

Disease

Relevance

Lipoic Acid Is a prosthetic group for many dehydrogenase in E. coli, and it is also needed for enzymes involved in the glycine cleavage system. [6] A key example of the use of lipoic acid as a prosthetic group is the E2 subunit of the pyruvate dehydrogenase complex. Lipoate attaches to a lysine on this subunit, and the sulfur on the ring of lipoic acid binds covalnetly with the incoming pyruvate to "shuttle" it to the SCoA complex for later use in the citric acid cycle. Lipoate protein Ligase A is the enzyme in e.Coli that attaches lipoate to the enzymes that need it. [7] Humans Have a homolog to this enzyme, called lipoyltransferase, and the two enzymes share between 31%-35% identity with each other. In contrast to the lipoate protein Ligase A, however, lipoyltransferase in humans is unable to catalyze the first part of the reaction in which an AMP is added to a lipoic acid.


Research has found that lipoate protein Ligase A proteins are present in fairly small numbers in an e.coli cell (less than 10 per cell). [8] Studies conducted on purified Lipoate protein Ligase found that the enzyme additionally requires Magnesium ions to functions properly, as well as lipoic acid and ATP. [9] Lipoate protein Ligase can use both the R and S enantiomers of Lipoate as substrates, though it has a higher affinity for (R)-Lipoate. [10] in addition to the enantiomers, other molecules similar in structure to lipoate, such as ocatnoate, can be incoporated into the enzymes active site, although with less affinity. [11]

Structural highlights

Lipoate protein Ligase is a monomer with a molecular weight of around 38,000 Da which corresponds to 337 amino acids in length. [12] The isoelectric point (pI) of the enzyme is 5.80, and the optimum pH for activity was determined by researchers to be either between pH 4.0 & 6.8 or Between pH 5.5-6.8 depending on whether the Lipoate substrate is oxidized or reduced respectively. [13] Experiments determined that the UV absorbance of the enzyme peaks at around 280nm. [14] researchers found the enzymes Km for ATP to be a range from 1.9-3.1 µM, and the Km for Lipoic acid to be from 1.6-5.0 µM. [15]

Researchers in Japan Successfully isolated lipoate Protein Ligase A from e.Coli and crystallized it in order to determine the structure. The team divided the protein into two main sections; a Larger N terminus section consisting of Amino Acids 1-244, and a smaller C terminal unit consisting of amino acids 253-337. There is a small segment of linker amino acids (245-252) that connect the two subunits. Researchers found that there is a space exposed to solution formed between these two subunit's, and this exposed portion is the active site to which lipoic acid binds. The sulfur and carbon ring of lipoic acid is held into place via hydrophobic interactions with Particular Leucine, Phenylalanine, and Alanine residues inside of the active site, as well as some non ring portions ofa serine side chain. The carboxylic acid on lipoate was determinedc to held in place by Hydrogen bonding formed with side chains of either Serine-72 or Arginine-140 (researchers saw both results in crystallized protein). Researchers hypothesized that other compounds similar to lipoate could bind to the active site because of the relatively weak forces that bind the substrate. In the crystalization experiment performed, the team was unable to determine the binding site of ATP on the enzyme, But their Data suggested that the serine-72 implicated in holding the carboxyl group of lipoate also plays an important role in catalyzing the reaction between ATP and lipoate. The resaerchers also state that this enzyme, as well as some homologs closely related to it, exhibit a potential ATP binding motif from Amino Acids 69-75. The researchers believe this portion can make both a positive charge and a space that allow the binding of ATP to the enzyme.

References

  1. ↑ Hanson, R. M., Prilusky, J., Renjian, Z., Nakane, T. and Sussman, J. L. (2013), JSmol and the Next-Generation Web-Based Representation of 3D Molecular Structure as Applied to Proteopedia. Isr. J. Chem., 53:207-216. doi:http://dx.doi.org/10.1002/ijch.201300024
  2. ↑ Herraez A. Biomolecules in the computer: Jmol to the rescue. Biochem Mol Biol Educ. 2006 Jul;34(4):255-61. doi: 10.1002/bmb.2006.494034042644. PMID:21638687 doi:10.1002/bmb.2006.494034042644
  3. ↑ Green DE, Morris TW, Green J, Cronan JE Jr, Guest JR. Purification and properties of the lipoate protein ligase of Escherichia coli. Biochem J. 1995 Aug 1;309 ( Pt 3):853-62. PMID:7639702
  4. ↑ Fujiwara K, Toma S, Okamura-Ikeda K, Motokawa Y, Nakagawa A, Taniguchi H. Crystal structure of lipoate-protein ligase A from Escherichia coli. Determination of the lipoic acid-binding site. J Biol Chem. 2005 Sep 30;280(39):33645-51. Epub 2005 Jul 25. PMID:16043486 doi:10.1074/jbc.M505010200
  5. ↑ Fujiwara K, Toma S, Okamura-Ikeda K, Motokawa Y, Nakagawa A, Taniguchi H. Crystal structure of lipoate-protein ligase A from Escherichia coli. Determination of the lipoic acid-binding site. J Biol Chem. 2005 Sep 30;280(39):33645-51. Epub 2005 Jul 25. PMID:16043486 doi:10.1074/jbc.M505010200
  6. ↑ Green DE, Morris TW, Green J, Cronan JE Jr, Guest JR. Purification and properties of the lipoate protein ligase of Escherichia coli. Biochem J. 1995 Aug 1;309 ( Pt 3):853-62. PMID:7639702
  7. ↑ Green DE, Morris TW, Green J, Cronan JE Jr, Guest JR. Purification and properties of the lipoate protein ligase of Escherichia coli. Biochem J. 1995 Aug 1;309 ( Pt 3):853-62. PMID:7639702
  8. ↑ Green DE, Morris TW, Green J, Cronan JE Jr, Guest JR. Purification and properties of the lipoate protein ligase of Escherichia coli. Biochem J. 1995 Aug 1;309 ( Pt 3):853-62. PMID:7639702
  9. ↑ Green DE, Morris TW, Green J, Cronan JE Jr, Guest JR. Purification and properties of the lipoate protein ligase of Escherichia coli. Biochem J. 1995 Aug 1;309 ( Pt 3):853-62. PMID:7639702
  10. ↑ Green DE, Morris TW, Green J, Cronan JE Jr, Guest JR. Purification and properties of the lipoate protein ligase of Escherichia coli. Biochem J. 1995 Aug 1;309 ( Pt 3):853-62. PMID:7639702
  11. ↑ Green DE, Morris TW, Green J, Cronan JE Jr, Guest JR. Purification and properties of the lipoate protein ligase of Escherichia coli. Biochem J. 1995 Aug 1;309 ( Pt 3):853-62. PMID:7639702
  12. ↑ Green DE, Morris TW, Green J, Cronan JE Jr, Guest JR. Purification and properties of the lipoate protein ligase of Escherichia coli. Biochem J. 1995 Aug 1;309 ( Pt 3):853-62. PMID:7639702
  13. ↑ Green DE, Morris TW, Green J, Cronan JE Jr, Guest JR. Purification and properties of the lipoate protein ligase of Escherichia coli. Biochem J. 1995 Aug 1;309 ( Pt 3):853-62. PMID:7639702
  14. ↑ Green DE, Morris TW, Green J, Cronan JE Jr, Guest JR. Purification and properties of the lipoate protein ligase of Escherichia coli. Biochem J. 1995 Aug 1;309 ( Pt 3):853-62. PMID:7639702
  15. ↑ Green DE, Morris TW, Green J, Cronan JE Jr, Guest JR. Purification and properties of the lipoate protein ligase of Escherichia coli. Biochem J. 1995 Aug 1;309 ( Pt 3):853-62. PMID:7639702
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