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Catalytic Site Atlas Version 2.2.12
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CSA entry for 1dki
Original Entry
Title:
Toxin
Compound:
Pyrogenic exotoxin b zymogen
Mutant:
Yes
UniProt/Swiss-Prot:
P26296-S
P26296-S
P26296-S
P26296-S
EC Class:
No EC number available
Other CSA Entries:
Overview of all sites for 1dki
Homologues of 1dki
Entries for UniProt/Swiss-Prot: P26296
Entries for UniProt/Swiss-Prot: P26296
Entries for UniProt/Swiss-Prot: P26296
Entries for UniProt/Swiss-Prot: P26296
Other Databases:
PDB entry: 1dki
PDBsum entry: 1dki
UniProt/Swiss-Prot: P26296
UniProt/Swiss-Prot: P26296
UniProt/Swiss-Prot: P26296
UniProt/Swiss-Prot: P26296
Literature Report:
Introduction:
Cysteine protease which is a virulance factor for many infectious diseases. It displays structural homology with papains despite having such low sequence identity with the superfamily that it merits being placed in a completely separate class.
Mechanism:
Cys 47 acts as the nucleophile for initial attack on the peptide substrate. The tetrahedral intermediate then collapses on protonation of the leaving group by His 195. This leaves an acyl-enzyme intermediate which is hydrolysed by an activated water molecule to complete the reaction.
Sites:

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Found by:
Literature reference 

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
SERA 47 0Sidechain, Backbone amide
ElectrostaticTransition state
NucleophileSubstrate
Cys 47 (appears as Ser 47 in pdb file) acts as nucleophile for initial attack on the peptide substrate to form an acyl enzyme intermediate. Also stabilises the tetrahedral intermediate via oxyanion hole.
Evidence from paper Evidence concerns Evidence type
PubMed ID 10681429 Current protein Structural similarity to homologue of known mechanism
PubMed ID 10681429 Current protein Mutagenesis of residue

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
HISA 195 0Sidechain
Acid/baseWater
Protonates leaving group to facilitate collapse of tetrahedral intermediate, then activates water to allow hydrolysis of acyl enzyme intermediate.
Evidence from paper Evidence concerns Evidence type
PubMed ID 10816533 Current protein Mutagenesis of residue
PubMed ID 10681429 Current protein Structural similarity to homologue of known mechanism
References:
1
Crystal structure of the zymogen form of the group A Streptococcus virulence factor SpeB: an integrin-binding cysteine protease.
T. F. Kagawa and J. C. Cooney and H. M. Baker and S. McSweeney and M. Liu and S. Gubba and J. M. Musser and E. N. Baker
Proc Natl Acad Sci U S A 97, (5) 2235-40, (2000).
10681429
2
Replacement of histidine 340 with alanine inactivates the group A Streptococcus extracellular cysteine protease virulence factor.
S. Gubba and V. Cipriano and J. M. Musser
Infect Immun 68, (6) 3716-9, (2000).
10816533
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