This old version of Proteopedia is provided for student assignments while the new version is undergoing repairs. Content and edits done in this old version of Proteopedia after March 1, 2026 will eventually be lost when it is retired in about June of 2026.
Apply for new accounts at the new Proteopedia. Your logins will work in both the old and new versions.
1ktw
From Proteopedia
OCA (Talk | contribs)
(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...)
Next diff →
Revision as of 23:48, 24 November 2007
|
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 CA, NA and CL 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
Page seeded by OCA on Sun Nov 25 01:56:05 2007
