6a0k | pdb_00006a0k

Cyclic alpha-maltosyl-(1-->6)-maltose hydrolase from Arthrobacter globiformis, complex with panose

spinqualitylabelsall models 6a0k, resolution 1.94Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 6a0k is a 2 chain structure with sequence from Arthrobacter globiformis. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 1.94Å Ligands: BGC, CA, GLC Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function D2YYE1_ARTGO Publication Abstract from PubMed Cyclic alpha-maltosyl-(1-->6)-maltose (CMM,cyclo-{-->6)-alpha-d-Glcp-(1-->4)-alpha-d-Glcp-(1-->6)-alpha-d-Glcp-(1-->4)- alpha-d-Glcp-(1-->}) is a cyclic glucotetrasaccharide with alternating alpha-1,4 and alpha-1,6 linkages. CMM is composed of two maltose units and is one of the smallest cyclic glucooligosaccharides. While CMM is resistant to usual amylases, it is efficiently hydrolyzed by CMM hydrolase (CMMase), belonging to subfamily 20 of glycoside hydrolase family 13 (GH13_20). Here, we determined the ligand-free crystal structure of CMMase from the soil-associated bacterium Arthrobacter globiformis and its structures in complex with maltose, panose, and CMM to elucidate the structural basis of substrate recognition by CMMase. The structures disclosed that although the monomer structure consists of three domains commonly adopted by GH13 and other alpha-amylase-related enzymes, CMMase forms a unique wing-like dimer structure. The complex structure with CMM revealed four specific subsites, namely, -3', -2, -1, and +1'. We also observed that the bound CMM molecule adopts a low-energy conformer compared with the X-ray structure of a single CMM crystal, also determined here. Comparison of the CMMase active site with those in other enzymes of the GH13_20 family revealed that three regions forming the wall of the cleft, denoted PYF (Pro-203/Tyr-204/Phe-205), CS (Cys-163/Ser-164), and Y (Tyr-168), are present only in CMMase and are involved in CMM recognition. Combinations of multiple substitutions in these regions markedly decreased the activity toward CMM, indicating that the specificity for this cyclic tetrasaccharide is supported by the entire shape of the pocket. In summary, our work uncovers the mechanistical basis for the highly specific interactions of CMMase with its substrate CMM. Structural features of a bacterial cyclic alpha-maltosyl-(1-->6)-maltose (CMM) hydrolase critical for CMM recognition and hydrolysis.,Kohno M, Arakawa T, Ota H, Mori T, Nishimoto T, Fushinobu S J Biol Chem. 2018 Sep 4. pii: RA118.004472. doi: 10.1074/jbc.RA118.004472. PMID:30181215 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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