1WDS

The role of an inner loop in the catalytic mechanism of soybean beta-amylase


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.64 Å
  • R-Value Free: 0.200 
  • R-Value Work: 0.171 
  • R-Value Observed: 0.171 

wwPDB Validation 3D Report Full Report



Literature

Structural analysis of threonine 342 mutants of soybean beta-amylase: role of a conformational change of the inner loop in the catalytic mechanism.

Kang, Y.N.Tanabe, A.Adachi, M.Utsumi, S.Mikami, B.

(2005) Biochemistry 44: 5106-5116

  • DOI: 10.1021/bi0476580
  • Structures With Same Primary Citation

  • PubMed Abstract: 
  • Two different conformations of the inner loop (residues 340-346) have been found in the soybean beta-amylase structures. In the "product form", the Thr 342 residue creates hydrogen bonds with Glu 186 (catalytic acid) and with the glucose residues at ...

    Two different conformations of the inner loop (residues 340-346) have been found in the soybean beta-amylase structures. In the "product form", the Thr 342 residue creates hydrogen bonds with Glu 186 (catalytic acid) and with the glucose residues at subsites -1 and +1, whereas most of those interactions are lost in the "apo form". To elucidate the relationship between the structural states of the inner loop and the catalytic mechanism, Thr 342 was mutated to Val, Ser, and Ala, respectively, and their crystal structures complexed with maltose were determined together with that of the apo enzyme at 1.27-1.64 A resolutions. The k(cat) values of the T342V, T342S, and T342A mutants decreased by 13-, 360-, and 1700-fold, respectively, compared to that of the wild-type enzyme. Whereas the inner loops in the wild-type/maltose and T342V/maltose complexes adopted the product form, those of the T342S/maltose and T342A/maltose complexes showed the apo form. Structural analyses suggested that the side chain of Thr 342 in product form plays an important role in distorting the sugar ring at subsite -1, stabilizing the deprotonated form of Glu 186, and grasping the glucose residue of the remaining substrate at subsite +1. The third hypothesis was proved by the fact that T342V hydrolyzes maltoheptaose following only multichain attack in contrast to multiple attack of the wild-type enzyme.


    Organizational Affiliation

    Laboratory of Food Quality Design and Development, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan.



Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Beta-amylaseA495Glycine maxMutation(s): 1 
Gene Names: BMY1
EC: 3.2.1.2
Find proteins for P10538 (Glycine max)
Explore P10538 
Go to UniProtKB:  P10538
Protein Feature View
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  • Reference Sequence
Oligosaccharides
Entity ID: 2
MoleculeChainsChain Length2D Diagram Glycosylation
alpha-D-glucopyranose-(1-4)-beta-D-glucopyranose
A
2 N/A
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
GLC
Query on GLC

Download CCD File 
A
alpha-D-glucopyranose
C6 H12 O6
WQZGKKKJIJFFOK-DVKNGEFBSA-N
 Ligand Interaction
SO4
Query on SO4

Download CCD File 
A
SULFATE ION
O4 S
QAOWNCQODCNURD-UHFFFAOYSA-L
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.64 Å
  • R-Value Free: 0.200 
  • R-Value Work: 0.171 
  • R-Value Observed: 0.171 
  • Space Group: P 31 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 84.615α = 90
b = 84.615β = 90
c = 143.109γ = 120
Software Package:
Software NamePurpose
CNSrefinement
SCALEdata reduction
SCALEPACKdata scaling
CNSphasing

Structure Validation

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Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2005-04-05
    Type: Initial release
  • Version 1.1: 2008-04-30
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2011-11-16
    Changes: Atomic model
  • Version 2.0: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Advisory, Atomic model, Data collection, Derived calculations, Structure summary