1e6p: Difference between revisions
New page: left|200px<br /><applet load="1e6p" size="450" color="white" frame="true" align="right" spinBox="true" caption="1e6p, resolution 1.70Å" /> '''CHITINASE B FROM SER... |
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[[Image:1e6p.gif|left|200px]]<br /><applet load="1e6p" size=" | [[Image:1e6p.gif|left|200px]]<br /><applet load="1e6p" size="350" color="white" frame="true" align="right" spinBox="true" | ||
caption="1e6p, resolution 1.70Å" /> | caption="1e6p, resolution 1.70Å" /> | ||
'''CHITINASE B FROM SERRATIA MARCESCENS INACTIVE MUTANT E144Q'''<br /> | '''CHITINASE B FROM SERRATIA MARCESCENS INACTIVE MUTANT E144Q'''<br /> | ||
==Overview== | ==Overview== | ||
Chitinase B (ChiB) from Serratia marcescens is a family 18 exo-chitinase | Chitinase B (ChiB) from Serratia marcescens is a family 18 exo-chitinase whose catalytic domain has a TIM-barrel fold with a tunnel-shaped active site. We have solved structures of three ChiB complexes that reveal details of substrate binding, substrate-assisted catalysis, and product displacement. The structure of an inactive ChiB mutant (E144Q) complexed with a pentameric substrate (binding in subsites -2 to +3) shows closure of the "roof" of the active site tunnel. It also shows that the sugar in the -1 position is distorted to a boat conformation, thus providing structural evidence in support of a previously proposed catalytic mechanism. The structures of the active enzyme complexed to allosamidin (an analogue of a proposed reaction intermediate) and of the active enzyme soaked with pentameric substrate show events after cleavage of the glycosidic bond. The latter structure shows reopening of the roof of the active site tunnel and enzyme-assisted product displacement in the +1 and +2 sites, allowing a water molecule to approach the reaction center. Catalysis is accompanied by correlated structural changes in the core of the TIM barrel that involve conserved polar residues whose functions were hitherto unknown. These changes simultaneously contribute to stabilization of the reaction intermediate and alternation of the pKa of the catalytic acid during the catalytic cycle. | ||
==About this Structure== | ==About this Structure== | ||
1E6P is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Serratia_marcescens Serratia marcescens] with SO4 and GOL as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http:// | 1E6P is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Serratia_marcescens Serratia marcescens] with <scene name='pdbligand=SO4:'>SO4</scene> and <scene name='pdbligand=GOL:'>GOL</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1E6P OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: Serratia marcescens]] | [[Category: Serratia marcescens]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Aalten, D | [[Category: Aalten, D M.F Van.]] | ||
[[Category: Eijsink, V | [[Category: Eijsink, V G.H.]] | ||
[[Category: Komander, D.]] | [[Category: Komander, D.]] | ||
[[Category: Synstad, B.]] | [[Category: Synstad, B.]] | ||
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[[Category: hydrolase]] | [[Category: hydrolase]] | ||
''Page seeded by [http:// | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:24:29 2008'' | ||
Revision as of 13:24, 21 February 2008
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CHITINASE B FROM SERRATIA MARCESCENS INACTIVE MUTANT E144Q
OverviewOverview
Chitinase B (ChiB) from Serratia marcescens is a family 18 exo-chitinase whose catalytic domain has a TIM-barrel fold with a tunnel-shaped active site. We have solved structures of three ChiB complexes that reveal details of substrate binding, substrate-assisted catalysis, and product displacement. The structure of an inactive ChiB mutant (E144Q) complexed with a pentameric substrate (binding in subsites -2 to +3) shows closure of the "roof" of the active site tunnel. It also shows that the sugar in the -1 position is distorted to a boat conformation, thus providing structural evidence in support of a previously proposed catalytic mechanism. The structures of the active enzyme complexed to allosamidin (an analogue of a proposed reaction intermediate) and of the active enzyme soaked with pentameric substrate show events after cleavage of the glycosidic bond. The latter structure shows reopening of the roof of the active site tunnel and enzyme-assisted product displacement in the +1 and +2 sites, allowing a water molecule to approach the reaction center. Catalysis is accompanied by correlated structural changes in the core of the TIM barrel that involve conserved polar residues whose functions were hitherto unknown. These changes simultaneously contribute to stabilization of the reaction intermediate and alternation of the pKa of the catalytic acid during the catalytic cycle.
About this StructureAbout this Structure
1E6P is a Single protein structure of sequence from Serratia marcescens with and as ligands. Full crystallographic information is available from OCA.
ReferenceReference
Structural insights into the catalytic mechanism of a family 18 exo-chitinase., van Aalten DM, Komander D, Synstad B, Gaseidnes S, Peter MG, Eijsink VG, Proc Natl Acad Sci U S A. 2001 Jul 31;98(16):8979-84. PMID:11481469
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