1NOW

Human lysosomal beta-hexosaminidase isoform B in complex with (2R,3R,4S,5R)-2-Acetamido-3,4-Dihydroxy-5-Hydroxymethyl-Piperidinium Chloride (GalNAc-isofagomine)


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.20 Å
  • R-Value Free: 0.218 
  • R-Value Work: 0.193 
  • R-Value Observed: 0.194 

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This is version 2.0 of the entry. See complete history


Literature

Crystal structure of Human beta-hexosaminidase B: Understanding the molecular basis of Sandhoff and Tay-Sachs disease

Mark, B.L.Mahuran, D.J.Cherney, M.M.Zhao, D.Knapp, S.James, M.N.G.

(2003) J Mol Biol 327: 1093-1109

  • DOI: https://doi.org/10.1016/s0022-2836(03)00216-x
  • Primary Citation of Related Structures:  
    1NOU, 1NOW, 1NP0

  • PubMed Abstract: 

    In humans, two major beta-hexosaminidase isoenzymes exist: Hex A and Hex B. Hex A is a heterodimer of subunits alpha and beta (60% identity), whereas Hex B is a homodimer of beta-subunits. Interest in human beta-hexosaminidase stems from its association with Tay-Sachs and Sandhoff disease; these are prototypical lysosomal storage disorders resulting from the abnormal accumulation of G(M2)-ganglioside (G(M2)). Hex A degrades G(M2) by removing a terminal N-acetyl-D-galactosamine (beta-GalNAc) residue, and this activity requires the G(M2)-activator, a protein which solubilizes the ganglioside for presentation to Hex A. We present here the crystal structure of human Hex B, alone (2.4A) and in complex with the mechanistic inhibitors GalNAc-isofagomine (2.2A) or NAG-thiazoline (2.5A). From these, and the known X-ray structure of the G(M2)-activator, we have modeled Hex A in complex with the activator and ganglioside. Together, our crystallographic and modeling data demonstrate how alpha and beta-subunits dimerize to form either Hex A or Hex B, how these isoenzymes hydrolyze diverse substrates, and how many documented point mutations cause Sandhoff disease (beta-subunit mutations) and Tay-Sachs disease (alpha-subunit mutations).


  • Organizational Affiliation

    Canadian Institutes of Heath Research Group in Protein Structure and Function, Department of Biochemistry, University of Alberta, T6G 2H7, Edmonton, Alt., Canada.


Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
beta-hexosaminidase beta chain
A, B
507Homo sapiensMutation(s): 0 
EC: 3.2.1.52
UniProt & NIH Common Fund Data Resources
Find proteins for P07686 (Homo sapiens)
Explore P07686 
Go to UniProtKB:  P07686
PHAROS:  P07686
GTEx:  ENSG00000049860 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP07686
Sequence Annotations
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  • Reference Sequence
Oligosaccharides

Help

Entity ID: 2
MoleculeChains Length2D Diagram Glycosylation3D Interactions
2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose
C, D
2N-Glycosylation
Glycosylation Resources
GlyTouCan:  G42666HT
GlyCosmos:  G42666HT
GlyGen:  G42666HT
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.20 Å
  • R-Value Free: 0.218 
  • R-Value Work: 0.193 
  • R-Value Observed: 0.194 
  • Space Group: P 61 2 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 112.391α = 90
b = 112.391β = 90
c = 397.309γ = 120
Software Package:
Software NamePurpose
REFMACrefinement
DENZOdata reduction
SCALEPACKdata scaling

Structure Validation

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Ligand Structure Quality Assessment 


Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2003-04-29
    Type: Initial release
  • Version 1.1: 2008-04-29
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Advisory, Derived calculations, Version format compliance
  • Version 1.3: 2012-11-07
    Changes: Derived calculations
  • Version 2.0: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Atomic model, Data collection, Derived calculations, Structure summary