6A0K

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

Summary for 6A0K

• Entry DOI: 10.2210/pdb6a0k/pdb
• Descriptor: Cyclic maltosyl-maltose hydrolase, alpha-D-glucopyranose-(1-6)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose, alpha-D-glucopyranose-(1-6)-alpha-D-glucopyranose-(1-4)-beta-D-glucopyranose, ... (5 entities in total)
• Functional Keywords: hydrolase
• Biological source: Arthrobacter globiformis
• Total number of polymer chains: 2
• Total formula weight: 105386.35

Authors

Kohno, M.,Arakawa, T.,Mori, T.,Nishimoto, T.,Fushinobu, S. (deposition date: 2018-06-05, release date: 2018-09-12, Last modification date: 2023-11-22)

Primary citation

Kohno, M.,Arakawa, T.,Ota, H.,Mori, T.,Nishimoto, T.,Fushinobu, S.
Structural features of a bacterial cyclic alpha-maltosyl-(1→6)-maltose (CMM) hydrolase critical for CMM recognition and hydrolysis.
J. Biol. Chem., 293:16874-16888, 2018

PubMed Abstract: Cyclic α-maltosyl-(1→6)-maltose (CMM, -{→6)-α-d-Glc-(1→4)-α-d-Glc-(1→6)-α-d-Glc-(1→4)-α-d-Glc-(1→})is a cyclic glucotetrasaccharide with alternating α-1,4 and α-1,6 linkages. CMM is composed of two maltose units and is one of the smallest cyclic glucooligosaccharides. Although 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 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 α-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 mechanistic basis for the highly specific interactions of CMMase with its substrate CMM.

PubMed: 30181215
DOI: 10.1074/jbc.RA118.004472

Experimental method

X-RAY DIFFRACTION (1.94 Å)