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433 a.a.
_CA
_CL
Key reference
Full text J Biol Chem 276:40202-40209 (2001) PubMed id: 11493601
The iota-carrageenase of Alteromonas fortis. A beta-helix fold-containing enzyme for the degradation of a highly polyanionic polysaccharide. G.Michel, L.Chantalat, E.Fanchon, B.Henrissat, B.Kloareg, O.Dideberg. ABSTRACT
Carrageenans are gel-forming hydrocolloids extracted from the cell walls of marine red algae. They consist of d-galactose residues bound by alternate alpha(1-->3) and beta(1-->4) linkages and substituted by one (kappa-carrageenan), two (iota-carrageenan), or three (lambda-carrageenan) sulfate-ester groups per disaccharide repeating unit. Both the kappa- and iota-carrageenan chains adopt ordered conformations leading to the formation of highly ordered aggregates of double-stranded helices. Several kappa-carrageenases and iota-carrageenases have been cloned from marine bacteria. Kappa-carrageenases belong to family 16 of the glycoside hydrolases, which essentially encompasses polysaccharidases specialized in the hydrolysis of the neutral polysaccharides such as agarose, laminarin, lichenan, and xyloglucan. In contrast, iota-carrageenases constitute a novel glycoside hydrolase structural family. We report here the crystal structure of Alteromonas fortis iota-carrageenase at 1.6 A resolution. The enzyme folds into a right-handed parallel beta-helix of 10 complete turns with two additional C-terminal domains. Glu(245), Asp(247), or Glu(310), in the cleft of the enzyme, are proposed as candidate catalytic residues. The protein contains one sodium and one chloride binding site and three calcium binding sites shown to be involved in stabilizing the enzyme structure.
Selected figure(s)
Figure 2.
Fig. 2. Solvent-flattened multiple anomalous diffraction electron density map at 1.6 Å resolution. Map contoured at 2.0of the N-terminal calcium-binding hairpin loop. Calcium ion and water molecules are indicated as yellow and red spheres, respectively. The oxygen, nitrogen, and carbon atoms in the protein are shown in red, blue, and yellow, respectively. This figure was created using O (23).
Figure 6.
Fig. 6.-Carrageenan recognition by
The above figures are reprinted by permission from the ASBMB: J Biol Chem (2001, 276, 40202-40209) copyright 2001. Figures were selected by an automated process.
Literature references that cite this PDB file's key reference
PubMed id Reference
16550377 G.Michel, P.Nyval-Collen, T.Barbeyron, M.Czjzek, and W.Helbert (2006).
Bioconversion of red seaweed galactans: a focus on bacterial agarases and carrageenases.Appl Microbiol Biotechnol, 71, 23-33.
15968068 S.A.Douthit, M.Dlakic, D.E.Ohman, and M.J.Franklin (2005).
Epimerase active domain of Pseudomonas aeruginosa AlgG, a protein that contains a right-handed beta-helix.J Bacteriol, 187, 4573-4583. The most recent references are shown first. Citation data come partly from CiteXplore and partly from an automated harvesting procedure. Note that this is likely to be only a partial list as not all journals are covered by either method. However, we are continually building up the citation data so more and more references will be included with time.
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