Sandbox 167: Difference between revisions
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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" />. | 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" />. | ||
[[Image:Structure_trihelix_barrel.jpg ]] | |||
[[Image:Structure_trihelix_barrel.jpg | thumb |none | upright=3.0 | Figure 1: 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.]] | |||
Note the position of the tri-helix in front of the β-barrel opening, blocking substrate entry. Under pH 8, the protonation states of the four histidines are thought to drive a conformational change that opens and expands the β-barrel. | Note the position of the tri-helix in front of the β-barrel opening, blocking substrate entry. Under pH 8, the protonation states of the four histidines are thought to drive a conformational change that opens and expands the β-barrel. | ||
== Luciferase Reaction == | == Luciferase Reaction == | ||
