1tlg
From Proteopedia
(New page: 200px<br /><applet load="1tlg" size="450" color="white" frame="true" align="right" spinBox="true" caption="1tlg, resolution 2.2Å" /> '''STRUCTURE OF A TUNICA...) |
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| - | [[Image:1tlg.jpg|left|200px]]<br /><applet load="1tlg" size=" | + | [[Image:1tlg.jpg|left|200px]]<br /><applet load="1tlg" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1tlg, resolution 2.2Å" /> | caption="1tlg, resolution 2.2Å" /> | ||
'''STRUCTURE OF A TUNICATE C-TYPE LECTIN COMPLEXED WITH D-GALACTOSE'''<br /> | '''STRUCTURE OF A TUNICATE C-TYPE LECTIN COMPLEXED WITH D-GALACTOSE'''<br /> | ||
==Overview== | ==Overview== | ||
| - | C-type lectins are calcium-dependent carbohydrate-recognising proteins. | + | C-type lectins are calcium-dependent carbohydrate-recognising proteins. Isothermal titration calorimetry of the C-type Polyandrocarpa lectin (TC14) from the tunicate Polyandrocarpa misakiensis revealed the presence of a single calcium atom per monomer with a dissociation constant of 2.6 microM, and confirmed the specificity of TC14 for D -galactose and related monosaccharides. We have determined the 2.2 A X-ray crystal structure of Polyandrocarpa lectin complexed with D -galactose. Analytical ultracentrifugation revealed that TC14 behaves as a dimer in solution. This is reflected by the presence of two molecules in the asymmetric unit with the dimeric interface formed by antiparallel pairing of the two N-terminal beta-strands and hydrophobic interactions. TC14 adopts a typical C-type lectin fold with differences in structure from other C-type lectins mainly in the diverse loop regions and in the second alpha-helix, which is involved in the formation of the dimeric interface. The D -galactose is bound through coordination of the 3 and 4-hydroxyl oxygen atoms with a bound calcium atom. Additional hydrogen bonds are formed directly between serine, aspartate and glutamate side-chains of the protein and the sugar 3 and 4-hydroxyl groups. Comparison of the galactose binding by TC14 with the mannose binding by rat mannose-binding protein reveals how monosaccharide specificity is achieved in this lectin. A tryptophan side-chain close to the binding site and the distribution of hydrogen-bond acceptors and donors around the 3 and 4-hydroxyl groups of the sugar are essential determinants of specificity. These elements are, however, arranged in a very different way than in an engineered galactose-specific mutant of MBPA. Possible biological functions can more easily be understood from the fact that TC14 is a dimer under physiological conditions. |
==About this Structure== | ==About this Structure== | ||
| - | 1TLG is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Polyandrocarpa_misakiensis Polyandrocarpa misakiensis] with GAL, CA and ZN as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http:// | + | 1TLG is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Polyandrocarpa_misakiensis Polyandrocarpa misakiensis] with <scene name='pdbligand=GAL:'>GAL</scene>, <scene name='pdbligand=CA:'>CA</scene> and <scene name='pdbligand=ZN:'>ZN</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1TLG OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Bycroft, M.]] | [[Category: Bycroft, M.]] | ||
| - | [[Category: Legge, G | + | [[Category: Legge, G B.]] |
| - | [[Category: Poget, S | + | [[Category: Poget, S F.]] |
| - | [[Category: Williams, R | + | [[Category: Williams, R L.]] |
[[Category: CA]] | [[Category: CA]] | ||
[[Category: GAL]] | [[Category: GAL]] | ||
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[[Category: galactose-specific]] | [[Category: galactose-specific]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 15:14:46 2008'' |
Revision as of 13:14, 21 February 2008
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STRUCTURE OF A TUNICATE C-TYPE LECTIN COMPLEXED WITH D-GALACTOSE
Overview
C-type lectins are calcium-dependent carbohydrate-recognising proteins. Isothermal titration calorimetry of the C-type Polyandrocarpa lectin (TC14) from the tunicate Polyandrocarpa misakiensis revealed the presence of a single calcium atom per monomer with a dissociation constant of 2.6 microM, and confirmed the specificity of TC14 for D -galactose and related monosaccharides. We have determined the 2.2 A X-ray crystal structure of Polyandrocarpa lectin complexed with D -galactose. Analytical ultracentrifugation revealed that TC14 behaves as a dimer in solution. This is reflected by the presence of two molecules in the asymmetric unit with the dimeric interface formed by antiparallel pairing of the two N-terminal beta-strands and hydrophobic interactions. TC14 adopts a typical C-type lectin fold with differences in structure from other C-type lectins mainly in the diverse loop regions and in the second alpha-helix, which is involved in the formation of the dimeric interface. The D -galactose is bound through coordination of the 3 and 4-hydroxyl oxygen atoms with a bound calcium atom. Additional hydrogen bonds are formed directly between serine, aspartate and glutamate side-chains of the protein and the sugar 3 and 4-hydroxyl groups. Comparison of the galactose binding by TC14 with the mannose binding by rat mannose-binding protein reveals how monosaccharide specificity is achieved in this lectin. A tryptophan side-chain close to the binding site and the distribution of hydrogen-bond acceptors and donors around the 3 and 4-hydroxyl groups of the sugar are essential determinants of specificity. These elements are, however, arranged in a very different way than in an engineered galactose-specific mutant of MBPA. Possible biological functions can more easily be understood from the fact that TC14 is a dimer under physiological conditions.
About this Structure
1TLG is a Single protein structure of sequence from Polyandrocarpa misakiensis with , and as ligands. Full crystallographic information is available from OCA.
Reference
The structure of a tunicate C-type lectin from Polyandrocarpa misakiensis complexed with D -galactose., Poget SF, Legge GB, Proctor MR, Butler PJ, Bycroft M, Williams RL, J Mol Biol. 1999 Jul 23;290(4):867-79. PMID:10398588
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