1sci

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{{STRUCTURE_1sci| PDB=1sci | SCENE= }}
{{STRUCTURE_1sci| PDB=1sci | SCENE= }}
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'''K236L mutant of hydroxynitrile lyase from Hevea brasiliensis'''
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===K236L mutant of hydroxynitrile lyase from Hevea brasiliensis===
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==Overview==
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The hydroxynitrile lyases (HNLs) from Hevea brasiliensis (HbHNL) and from Manihot esculenta (MeHNL) are both members of the alpha/beta-hydrolase superfamily. Mechanistic proposals have been put forward in the past for both enzymes; they differed with respect to the role of the active-site lysine residue for which a catalytic function was claimed for the Hevea enzyme but denied for the Manihot enzyme. We applied a freeze-quench method to prepare crystals of the complex of HbHNL with the biological substrate acetone cyanohydrin and determined its three-dimensional structure. Site-directed mutagenesis was used to prepare the mutant K236L, which is inactive although its three-dimensional structure is similar to the wild-type enzyme. However, the structure of the K236L-acetone cyanohydrin complex shows the substrate in a different orientation from the wild-type complex. Finite difference Poisson-Boltzmann calculations show that in the absence of Lys(236) the catalytic base His(235) would be protonated at neutral pH. All of this suggests that Lys(236) is instrumental for catalysis in several ways, i.e. by correctly positioning the substrate, by stabilizing the negatively charged reaction product CN(-), and by modulating the basicity of the catalytic base. These data complete the elucidation of the reaction mechanism of alpha/beta-hydrolase HNLs, in which the catalytic triad acts as a general base rather than as a nucleophile; proton abstraction from the substrate is performed by the serine, and reprotonation of the product cyanide is performed by the histidine residues. Together with a threonine side chain, the active-site serine and lysine are also involved in substrate binding.
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(as it appears on PubMed at http://www.pubmed.gov), where 14998991 is the PubMed ID number.
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{{ABSTRACT_PUBMED_14998991}}
==About this Structure==
==About this Structure==
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==Reference==
==Reference==
Reaction mechanism of hydroxynitrile lyases of the alpha/beta-hydrolase superfamily: the three-dimensional structure of the transient enzyme-substrate complex certifies the crucial role of LYS236., Gruber K, Gartler G, Krammer B, Schwab H, Kratky C, J Biol Chem. 2004 May 7;279(19):20501-10. Epub 2004 Mar 3. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/14998991 14998991]
Reaction mechanism of hydroxynitrile lyases of the alpha/beta-hydrolase superfamily: the three-dimensional structure of the transient enzyme-substrate complex certifies the crucial role of LYS236., Gruber K, Gartler G, Krammer B, Schwab H, Kratky C, J Biol Chem. 2004 May 7;279(19):20501-10. Epub 2004 Mar 3. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/14998991 14998991]
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Atomic resolution crystal structure of hydroxynitrile lyase from Hevea brasiliensis., Gruber K, Gugganig M, Wagner UG, Kratky C, Biol Chem. 1999 Jul-Aug;380(7-8):993-1000. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/10494852 10494852]
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Three-dimensional structures of enzyme-substrate complexes of the hydroxynitrile lyase from Hevea brasiliensis., Zuegg J, Gruber K, Gugganig M, Wagner UG, Kratky C, Protein Sci. 1999 Oct;8(10):1990-2000. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/10548044 10548044]
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Mechanism of cyanogenesis: the crystal structure of hydroxynitrile lyase from Hevea brasiliensis., Wagner UG, Hasslacher M, Griengl H, Schwab H, Kratky C, Structure. 1996 Jul 15;4(7):811-22. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/8805565 8805565]
[[Category: Hevea brasiliensis]]
[[Category: Hevea brasiliensis]]
[[Category: Single protein]]
[[Category: Single protein]]
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[[Category: Alpha-beta hydrolase fold]]
[[Category: Alpha-beta hydrolase fold]]
[[Category: Catalytic triad]]
[[Category: Catalytic triad]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Jul 27 15:26:21 2008''

Revision as of 12:26, 27 July 2008

Image:1sci.png

Template:STRUCTURE 1sci

K236L mutant of hydroxynitrile lyase from Hevea brasiliensis

Template:ABSTRACT PUBMED 14998991

About this Structure

1SCI is a Single protein structure of sequence from Hevea brasiliensis. Full crystallographic information is available from OCA.

Reference

Reaction mechanism of hydroxynitrile lyases of the alpha/beta-hydrolase superfamily: the three-dimensional structure of the transient enzyme-substrate complex certifies the crucial role of LYS236., Gruber K, Gartler G, Krammer B, Schwab H, Kratky C, J Biol Chem. 2004 May 7;279(19):20501-10. Epub 2004 Mar 3. PMID:14998991

Atomic resolution crystal structure of hydroxynitrile lyase from Hevea brasiliensis., Gruber K, Gugganig M, Wagner UG, Kratky C, Biol Chem. 1999 Jul-Aug;380(7-8):993-1000. PMID:10494852

Three-dimensional structures of enzyme-substrate complexes of the hydroxynitrile lyase from Hevea brasiliensis., Zuegg J, Gruber K, Gugganig M, Wagner UG, Kratky C, Protein Sci. 1999 Oct;8(10):1990-2000. PMID:10548044

Mechanism of cyanogenesis: the crystal structure of hydroxynitrile lyase from Hevea brasiliensis., Wagner UG, Hasslacher M, Griengl H, Schwab H, Kratky C, Structure. 1996 Jul 15;4(7):811-22. PMID:8805565

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