4s3p

Amylomaltase MalQ from Escherichia coli, apo structure

spinqualitylabelsall models 4s3p, resolution 2.80Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4s3p is a 2 chain structure. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Related: 4s3q, 4s3r Activity: 4-alpha-glucanotransferase, with EC number 2.4.1.25 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum Publication Abstract from PubMed Amylomaltase MalQ is essential for the metabolism of maltose and maltodextrins in Escherichia coli. It catalyzes transglycosylation/disproportionation reactions in which glycosyl or dextrinyl units are transferred among linear maltodextrins of various lengths. To elucidate the molecular basis of transglycosylation by MalQ, we have determined three crystal structures of this enzyme, i.e. the apo form, its complex with maltose and an inhibitor complex with the transition state analog acarviosine-glucose-acarbose, at resolutions down to 2.1 A. MalQ represents the first example of a mesophilic bacterial amylomaltase and exhibits an N-terminal extension of about 140 residues, in contrast with previously described thermophilic enzymes. This moiety seems unique to amylomaltases from Enterobacteriaceae and folds into two distinct subdomains that associate with different parts of the catalytic core. Intriguingly, the three MalQ crystal structures appear to correspond to distinct states of this enzyme, revealing considerable conformational changes during the catalytic cycle. In particular, the inhibitor complex highlights the requirement of both a 3-OH group and a 4-OH group (or alpha1-4-glycosidic bond) at the acceptor subsite +1 for the catalytically competent orientation of the acid/base catalyst Glu496. Using an HPLC-based MalQ enzyme assay, we could demonstrate that the equilibrium concentration of maltodextrin products depends on the length of the initial substrate: with increasing number of glycosidic bonds less glucose is formed. Thus, both structural and enzymatic data are consistent with the extremely low hydrolysis rates observed for amylomaltases and underline the importance of MalQ for the metabolism of maltodextrins in E. coli. Structural basis for the interconversion of maltodextrins by MalQ, the amylomaltase of Escherichia coli.,Weiss SC, Skerra A, Schiefner A J Biol Chem. 2015 Jul 2. pii: jbc.M115.667337. PMID:26139606 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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