4okd

Crystal Structure of Chlamydomonas reinhardtii Isoamylase 1 (ISA1) in complex with maltoheptaose

spinqualitylabelsall models 4okd, resolution 2.40Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4okd is a 2 chain structure with sequence from Chlamydomonas reinhardtii. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.4Å Ligands: GLC, PRD_900009 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function Q7X8Q2_CHLRE Publication Abstract from PubMed The starch debranching enzymes isoamylase 1 and 2 (ISA1 & ISA2) are known to exist in a large complex and are involved in the biosynthesis and crystallization of starch. It is suggested that the function of the complex is to remove misplaced branches of growing amylopectin molecules, which would otherwise prevent the association and crystallization of adjacent linear chains. Here, we investigate the function of ISA1 and ISA2 from starch producing alga Chlamydomonas. Through complementation studies, we confirm that the STA8 locus encodes for ISA2 and sta8 mutants lack the ISA1/ISA2 heteromeric complex. However, mutants retain a functional dimeric ISA1 that is able to partly sustain starch synthesis in vivo. To better characterize ISA1, we have overexpressed and purified ISA1 from Chlamydomonas reinhardtii (CrISA1) and solved the crystal structure to 2.3 A and in complex with maltoheptaose to 2.4 A. Analysis of the homodimeric CrISA1 structure reveals a unique elongated structure with monomers connected end-to-end. The crystal complex reveals details about the mechanism of branch binding that explains the low activity of CrISA1 towards tightly spaced branches and reveals the presence of additional secondary surface carbohydrate binding sites. Crystal structure of the Chlamydomonas starch debranching enzyme isoamylase ISA1 reveals insights into the mechanism of branch trimming and complex assembly.,Sim L, Beeren SR, Findinier J, Dauvillee D, Ball S, Henriksen A, Palcic MM J Biol Chem. 2014 Jul 3. pii: jbc.M114.565044. PMID:24993830 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Mannose-binding protein

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