Sandbox Reserved 993: Difference between revisions
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== Structure == | == Structure == | ||
''Photinus pyralis'' luciferase a monomeric enzyme composed of 550 residues, resulting in a 62 kDa molecular weight. The protein is divided into two <scene name='69/691535/ | ''Photinus pyralis'' luciferase a monomeric enzyme composed of 550 residues, resulting in a 62 kDa molecular weight. The protein is divided into two <scene name='69/691535/Colored_domains/2'>domains</scene> (the N-terminal domain and the C-terminal domain) by a wide cleft. Although not shown in the model, the domains are connected by a flexible loop structure. The N-terminal domain (residues 4-436) is much larger than the C-terminal domain (residues 440-544) and is formed by an antiparallel β-barrel (green) as well as two β-sheet subdomains (pink and blue) that create an αβαβα tertiary structure.<ref name=Conti1996 /> The C-terminal domain, on the other hand, is folded into an α+β tertiary structure (yellow).<ref name=Conti1996 /> Currently, it is thought that the active site is located at the surfaces where the domains meet and that a conformation change occurs after the substrates are bound in which the domains come together and enclose the substrates.<ref name=Conti1996 /><ref name=Marques2009>Marques S.M. and Esteves da Silva J.C.G. (2009) "Firefly bioluminescence: mechanistic approach of luciferase catalyzed reactions", IUBMB Life 61(1): 6-17. doi: 10.1002/iub.134</ref> This enclosement creates a hydrophobic environment which prevents light production from being quenched by water.<ref name=Conti1996 /><ref name=Bedford2012>Bedford R., LePage D., Hoffman R., Kennedy S., Gutschenritter T., Bull L., Sujijantarat N., DiCesare J.C., and Sheaff R.J. (2012) "Luciferase inhibition by a novel naphthoquinone", J. Photochem. Photobiol., B 107: 55-64. doi: 10.1016/j.jphotobiol.2011.11.008</ref> | ||
A model for the active site of ''Photinus pyralis'' luciferase was proposed by Branchini and colleagues in 1998 and has held up to more recent data.<ref name=Zako2003>Zako T., Ayabe K., Aburatani T., Kamiya N., Kitayama A., Ueda H., and Nagamune T. (2003) "Luminescent and substrate binding activities of firefly luciferase N-terminal domain", 1649(2): 183-189. doi: 10.1016/S1570-9639(03)00179-1</ref> In this model, the enzyme contains a binding pocket for ATP as well as a binding pocket for luciferin. The binding pocket for ATP is formed by the residues 316GAP318, 339GYGL342, and V362, and binds to the adenine ring.<ref name=Branchini1998>Branchini B.R., Magyar R.A., Murtiashaw M.H., Anderson S.M., and Zimmer M. (1998) "Site-directed mutagenesis of Histidine 245 in firefly luciferase: a proposed model of the active site", Biochemistry 37(44): 15311-15319. doi: 10.1021/bi981150d</ref> The luciferin binding pocket is comprised of the residues 341GLT343, 346TSA348, 245HHGFGMT251 (helix), 315GGA317 (loop), and R218.<ref name=Branchini1998 /> A model of the active site with a bound luciferase inhibitor (PTC128) is shown <scene name='69/691535/Active_site_structure/2'>here</scene> (blue=ATP binding pocket, purple=luciferin binding pocket, and green=residues shared by binding pockets). The S314-L319 loop and Q338-A348 region were found to be in different positions when substrates were bound.<ref name=Branchini1998 /> Since the loop blocks both of the binding pockets when in the unbound state, it makes sense that a conformational change in the loop must occur.<ref name=Branchini1998 /> | A model for the active site of ''Photinus pyralis'' luciferase was proposed by Branchini and colleagues in 1998 and has held up to more recent data.<ref name=Zako2003>Zako T., Ayabe K., Aburatani T., Kamiya N., Kitayama A., Ueda H., and Nagamune T. (2003) "Luminescent and substrate binding activities of firefly luciferase N-terminal domain", 1649(2): 183-189. doi: 10.1016/S1570-9639(03)00179-1</ref> In this model, the enzyme contains a binding pocket for ATP as well as a binding pocket for luciferin. The binding pocket for ATP is formed by the residues 316GAP318, 339GYGL342, and V362, and binds to the adenine ring.<ref name=Branchini1998>Branchini B.R., Magyar R.A., Murtiashaw M.H., Anderson S.M., and Zimmer M. (1998) "Site-directed mutagenesis of Histidine 245 in firefly luciferase: a proposed model of the active site", Biochemistry 37(44): 15311-15319. doi: 10.1021/bi981150d</ref> The luciferin binding pocket is comprised of the residues 341GLT343, 346TSA348, 245HHGFGMT251 (helix), 315GGA317 (loop), and R218.<ref name=Branchini1998 /> A model of the active site with a bound luciferase inhibitor (PTC128) is shown <scene name='69/691535/Active_site_structure/2'>here</scene> (blue=ATP binding pocket, purple=luciferin binding pocket, and green=residues shared by binding pockets). The S314-L319 loop and Q338-A348 region were found to be in different positions when substrates were bound.<ref name=Branchini1998 /> Since the loop blocks both of the binding pockets when in the unbound state, it makes sense that a conformational change in the loop must occur.<ref name=Branchini1998 /> | ||