1O7A image
Deposition Date 2002-10-29
Release Date 2003-10-23
Last Version Date 2024-11-13
Entry Detail
PDB ID:
1O7A
Keywords:
Title:
Human beta-Hexosaminidase B
Biological Source:
Source Organism:
HOMO SAPIENS (Taxon ID: 9606)
Host Organism:
Method Details:
Experimental Method:
Resolution:
2.25 Å
R-Value Free:
0.23
R-Value Work:
0.19
R-Value Observed:
0.19
Space Group:
P 31 2 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Molecule:BETA-HEXOSAMINIDASE BETA CHAIN
Gene (Uniprot):HEXB
Chain IDs:A, B, C, D, E, F
Chain Length:515
Number of Molecules:6
Biological Source:HOMO SAPIENS
Modified Residue
Compound ID Chain ID Parent Comp ID Details 2D Image
ASN A ASN GLYCOSYLATION SITE
Primary Citation
The X-Ray Crystal Structure of Human Beta-Hexosaminidase B Provides New Insights Into Sandhoff Disease
J.Mol.Biol. 328 669 ? (2003)
PMID: 12706724 DOI: 10.1016/S0022-2836(03)00311-5

Abstact

Human lysosomal beta-hexosaminidases are dimeric enzymes composed of alpha and beta-chains, encoded by the genes HEXA and HEXB. They occur in three isoforms, the homodimeric hexosaminidases B (betabeta) and S (alphaalpha), and the heterodimeric hexosaminidase A (alphabeta), where dimerization is required for catalytic activity. Allelic variations in the HEXA and HEXB genes cause the fatal inborn errors of metabolism Tay-Sachs disease and Sandhoff disease, respectively. Here, we present the crystal structure of a complex of human beta-hexosaminidase B with a transition state analogue inhibitor at 2.3A resolution (pdb 1o7a). On the basis of this structure and previous studies on related enzymes, a retaining double-displacement mechanism for glycosyl hydrolysis by beta-hexosaminidase B is proposed. In the dimer structure, which is derived from an analysis of crystal packing, most of the mutations causing late-onset Sandhoff disease reside near the dimer interface and are proposed to interfere with correct dimer formation. The structure reported here is a valid template also for the dimeric structures of beta-hexosaminidase A and S.

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Protein

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Disease

Primary Citation of related structures