Sandbox 167: Difference between revisions
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== Introduction == | == Introduction == | ||
''Lingulodinium polyedrum'', a marine dinoflagellate often responsible for red tide, posesses a unique luciferase enyzme. When mechanically stimulated, the organism uses this enzyme to produce a blue light, likely for use in quorum sensing. Other luciferase enzymes typically produce green-yellow to red light. Also, while all luciferase enzymes produce light through oxidation of luciferin, the biochemical mechanism by which this is achieved is different, so the lack of similarity to firefly and bacterial luciferases is expected. | |||
In ''L. polyedrum'', the luciferase enzyme is a single polypeptide chain folded into 3 similiar domains. Interestingly, all three domains appear to be distinct luciferase centres with their own catalytic activities <ref name="main">PMID:15665092</ref> | In ''L. polyedrum'', the luciferase enzyme is a single polypeptide chain folded into 3 similiar domains. Interestingly, all three domains appear to be distinct luciferase centres with their own catalytic activities <ref name="main">PMID:15665092</ref> | ||
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== Structure == | == Structure == | ||
Composed of residues 868-1218, domain 3 (D3) also consists of a 20aa C-terminal unresolved domain. Containing 7 α-helices and 16 β-strands, D3 is further organized into subdomains. The main portion of the enzyme appears to be a β-barrel structure composed of 10 anti-parallel strands connected via a Gly rich sequence to a 3 helix bundle. This bundle is stabilized by a hydrophobic core region as well as a multitude of H-bonding patterns<ref name="main" />. The β-barrel structure actually has some homology with the human muscle fatty acid binding protein (m-FABP, pdb= 1HMT). This, and other related proteins, form a "β-clam" subdomain structure for binding of hydrophobic molecules. However, other known β-clam structures do not possess enzymatic activity<ref name="main" />. | |||
Cropped Pymol image of 1vpr highlighting the β-barrel structure and tri-helix. The four histidine residues implied in pH-dependant activity regulation are highlighted in pink. | Cropped Pymol image of 1vpr highlighting the β-barrel structure and tri-helix. The four histidine residues implied in pH-dependant activity regulation are highlighted in pink. | ||
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== Luciferase Reaction == | == Luciferase Reaction == | ||
Typically, luciferases produce light through a high energy complex with a luciferin cofactor, and Mg-ATP. The structure of luciferin is different from organism to organism, and in ''L. polyedrum'', is a chlorophyll-derived open-tetrapyrrole. Below is the dinoflagellate luciferase reaction, showing the oxidation site. | |||
[[Image:Luciferase_reaction.jpg]] | [[Image:Luciferase_reaction.jpg]] | ||