1ktw
From Proteopedia
(New page: 200px<br /><applet load="1ktw" size="450" color="white" frame="true" align="right" spinBox="true" caption="1ktw, resolution 2.00Å" /> '''IOTA-CARRAGEENASE CO...) |
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| - | [[Image:1ktw.gif|left|200px]]<br /><applet load="1ktw" size=" | + | [[Image:1ktw.gif|left|200px]]<br /><applet load="1ktw" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1ktw, resolution 2.00Å" /> | caption="1ktw, resolution 2.00Å" /> | ||
'''IOTA-CARRAGEENASE COMPLEXED TO IOTA-CARRAGEENAN FRAGMENTS'''<br /> | '''IOTA-CARRAGEENASE COMPLEXED TO IOTA-CARRAGEENAN FRAGMENTS'''<br /> | ||
==Overview== | ==Overview== | ||
| - | iota-Carrageenans are sulfated 1,3-alpha-1,4-beta-galactans from the cell | + | iota-Carrageenans are sulfated 1,3-alpha-1,4-beta-galactans from the cell walls of red algae, which auto-associate into crystalline fibers made of aggregates of double-stranded helices. iota-Carrageenases, which constitute family 82 of glycoside hydrolases, fold into a right-handed beta-helix. Here, the structure of Alteromonas fortis iota-carrageenase bound to iota-carrageenan fragments was solved at 2.0A resolution (PDB 1KTW). The enzyme holds a iota-carrageenan tetrasaccharide (subsites +1 to +4) and a disaccharide (subsites -3, -4), thus providing the first direct determination of a 3D structure of iota-carrageenan. Electrostatic interactions between basic protein residues and the sulfate substituents of the polysaccharide chain dominate iota-carrageenan recognition. Glu245 and Asp247 are the proton donor and the base catalyst, respectively. C-terminal domain A, which was highly flexible in the native enzyme structure, adopts a alpha/beta-fold, also found in DNA/RNA-binding domains. In the substrate-enzyme complex, this polyanion-binding module shifts toward the beta-helix groove, forming a tunnel. Thus, from an open conformation which allows for the initial endo-attack of iota-carrageenan chains, the enzyme switches to a closed-tunnel form, consistent with its highly processive character, as seen from the electron-microscopy analysis of the degradation of iota-carrageenan fibers. |
==About this Structure== | ==About this Structure== | ||
| - | 1KTW is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Alteromonas_sp._atcc_43554 Alteromonas sp. atcc 43554] with CA, NA and CL as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Iota-carrageenase Iota-carrageenase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.157 3.2.1.157] Full crystallographic information is available from [http:// | + | 1KTW is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Alteromonas_sp._atcc_43554 Alteromonas sp. atcc 43554] with <scene name='pdbligand=CA:'>CA</scene>, <scene name='pdbligand=NA:'>NA</scene> and <scene name='pdbligand=CL:'>CL</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Iota-carrageenase Iota-carrageenase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.157 3.2.1.157] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1KTW OCA]. |
==Reference== | ==Reference== | ||
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[[Category: iota-carrageenan double helix degradation]] | [[Category: iota-carrageenan double helix degradation]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 13:37:52 2008'' |
Revision as of 11:37, 21 February 2008
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IOTA-CARRAGEENASE COMPLEXED TO IOTA-CARRAGEENAN FRAGMENTS
Overview
iota-Carrageenans are sulfated 1,3-alpha-1,4-beta-galactans from the cell walls of red algae, which auto-associate into crystalline fibers made of aggregates of double-stranded helices. iota-Carrageenases, which constitute family 82 of glycoside hydrolases, fold into a right-handed beta-helix. Here, the structure of Alteromonas fortis iota-carrageenase bound to iota-carrageenan fragments was solved at 2.0A resolution (PDB 1KTW). The enzyme holds a iota-carrageenan tetrasaccharide (subsites +1 to +4) and a disaccharide (subsites -3, -4), thus providing the first direct determination of a 3D structure of iota-carrageenan. Electrostatic interactions between basic protein residues and the sulfate substituents of the polysaccharide chain dominate iota-carrageenan recognition. Glu245 and Asp247 are the proton donor and the base catalyst, respectively. C-terminal domain A, which was highly flexible in the native enzyme structure, adopts a alpha/beta-fold, also found in DNA/RNA-binding domains. In the substrate-enzyme complex, this polyanion-binding module shifts toward the beta-helix groove, forming a tunnel. Thus, from an open conformation which allows for the initial endo-attack of iota-carrageenan chains, the enzyme switches to a closed-tunnel form, consistent with its highly processive character, as seen from the electron-microscopy analysis of the degradation of iota-carrageenan fibers.
About this Structure
1KTW is a Single protein structure of sequence from Alteromonas sp. atcc 43554 with , and as ligands. Active as Iota-carrageenase, with EC number 3.2.1.157 Full crystallographic information is available from OCA.
Reference
The structural bases of the processive degradation of iota-carrageenan, a main cell wall polysaccharide of red algae., Michel G, Helbert W, Kahn R, Dideberg O, Kloareg B, J Mol Biol. 2003 Nov 28;334(3):421-33. PMID:14623184
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