1ITC

Beta-Amylase from Bacillus cereus var. mycoides Complexed with Maltopentaose

Summary for 1ITC

• Entry DOI: 10.2210/pdb1itc/pdb
• Related: 1ITD 1ITJ 5BCA
• Related PRD ID: PRD_900001 PRD_900009 PRD_900010 PRD_900030
• Descriptor: Beta-Amylase, alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose, alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose, ... (9 entities in total)
• Functional Keywords: hydrolase, beta-amylase, raw-starch binding domain, maltopentaose, catalytic-site mutant
• Biological source: Bacillus cereus
• Total number of polymer chains: 1
• Total formula weight: 60838.71

Authors

Miyake, H.,Kurisu, G.,Kusunoki, M.,Nishimura, S.,Kitamura, S.,Nitta, Y. (deposition date: 2002-01-17, release date: 2003-05-27, Last modification date: 2024-10-30)

Primary citation

Miyake, H.,Kurisu, G.,Kusunoki, M.,Nishimura, S.,Kitamura, S.,Nitta, Y.
Crystal Structure of a Catalytic Site Mutant of beta-Amylase from Bacillus cereus var. mycoides Cocrystallized with Maltopentaose
BIOCHEMISTRY, 42:5574-5581, 2003

PubMed Abstract: The X-ray crystal structure of a catalytic site mutant of beta-amylase, E172A (Glu172 --> Ala), from Bacillus cereus var. mycoides complexed with a substrate, maltopentaose (G5), and the wild-type enzyme complexed with maltose were determined at 2.1 and 2.0 A resolution, respectively. Clear and continuous density corresponding to G5 was observed in the active site of E172A, and thus, the substrate, G5, was not hydrolyzed. All glucose residues adopted a relaxed (4)C(1) conformation, and the conformation of the maltose unit for Glc2 and Glc3 was much different from those of other maltose units, where each glucose residue of G5 is named Glc1-Glc5 (Glc1 is at the nonreducing end). A water molecule was observed 3.3 A from the C1 atom of Glc2, and 3.0 A apart from the OE1 atom of Glu367 which acts as a general base. In the wild-type enzyme-maltose complex, two maltose molecules bind at subsites -2 and -1 and at subsites +1 and +2 in tandem. The conformation of the maltose molecules was similar to that of the condensation product of soybean beta-amylase, but differed from that of G5 in E172A. When the substrate flips between Glc2 and Glc3, the conformational energy of the maltose unit was calculated to be 20 kcal/mol higher than that of the cis conformation by MM3. We suggest that beta-amylase destabilizes the bond that is to be broken in the ES complex, decreasing the activation energy, DeltaG(++), which is the difference in free energy between this state and the transition state.

PubMed: 12741813
DOI: 10.1021/bi020712x

Experimental method

X-RAY DIFFRACTION (2.1 Å)