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Search The CSA
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Catalytic Site Atlas

CSA LITERATURE entry for 1btl

E.C. namebeta-lactamase
SpeciesEscherichia coli (Bacteria)
E.C. Number (IntEnz) 3.5.2.6
CSA Homologues of 1btlThere are 165 Homologs
CSA Entries With UniProtID P62593
CSA Entries With EC Number 3.5.2.6
PDBe Entry 1btl
PDBSum Entry 1btl
MACiE Entry M0002

Literature Report

IntroductionThe E.Coli derived Class A Beta lactamase acts to hydrolyse the endocyclic amide bond of B lactam substrate in a two step mechanism: acylation (covalent attachment of the beta-lactam to an active site serine, Ser70), followed by deacylation.
MechansimThe beta-lactamase mechanism consists of two steps: acylation (covalent attachment of the beta-lactam to an active site serine, Ser70), followed by deacylation.In the first step, initial acid catalysed protonation of the B lactam is energetically favoured, which is then followed by base catalysed nucleophilic attack from Ser70 at the carbonyl carbon of the lactam, where activation of Ser70 by Glu166 and nucleophilic attack happen simultaneously. The protonation at lactam N(1) is catalysed within a hydrogen bonded cluster involving the 2-carboxylate group in the substrate, side chains S130, K 234 and a exogenous solvent molecule. The nucleophilic Ser70 has been shown to approach the butterfly cadge beta-lactam structure from the exo face, its activity directed by interactions with the surrounding ion pairs.

Reaction

Catalytic Sites for 1btl

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
SerA7068macie:sideChainThe residue acts as a nucleophile towards the beta lactam substrate carbonyl group, with activation from acid/base interaction with a conserved hydrolytic water molecule, in turn interacting with Glu166.The backbone NH acts as part of an oxyanion hole, stabilising the transition state. The residue forms an ion pair with Lys 73.
SerA7068macie:mainChainAmideThe residue acts as a nucleophile towards the beta lactam substrate carbonyl group, with activation from acid/base interaction with a conserved hydrolytic water molecule, in turn interacting with Glu166.The backbone NH acts as part of an oxyanion hole, stabilising the transition state. The residue forms an ion pair with Lys 73.
GluA166164macie:sideChainIn acylation the residue acts as a general base towards a structurally conserved water molecule,leading to the deprotonation of Ser70 (proton relay). In deacylation, Glu 166 abstracts a proton from a water molecule, activating a nucleophile for attack at the substrate carbon linked to the gamma oxygen of S 70. The residue is hydrogen bonded to Lys 73.
SerA130128macie:sideChainThe residue is implicated in catalytic action within a hydrogen bonding network which mediates protonation of the substrate nitrogen through proton relay.The residue interacts with K234 through hydrogen bonding and the substrate oxygen 12, held within the carboxylate group.
LysA7371macie:sideChainThe residue forms an ion pair with S70,which is involved in the proton transfer event.The residue remains protonated through out the reaction, and is thought to be involved in directing the S 70 hydroxyl group for effective catalysis. The residue interacts with Glu 166 via hydrogen bonding.
LysA234232macie:sideChainThe residue is implicated in the initial protonation of the substrate N(1) by interaction with S130 through hydrogen bonding.
AlaA237235macie:mainChainAmideBackbone of the residue forms an oxyanion hole in conjunction with the backbone of residue S70 to stabilise the anionic tetrahedral intermediate.

Literature References

Notes:
Lamotte-Brasseur J
Mechanism of acyl transfer by the class A serine beta-lactamase of Streptomyces albus G.
Biochem J 1991 279 ( Pt 1) 213-221
PubMed: 1930139
Damblon C
The catalytic mechanism of beta-lactamases: NMR titration of an active-site lysine residue of the TEM-1 enzyme.
Proc Natl Acad Sci U S A 1996 93 1747-1752
PubMed: 8700829
Hermann JC
Identification of Glu166 as the general base in the acylation reaction of class A beta-lactamases through QM/MM modeling.
J Am Chem Soc 2003 125 9590-9591
PubMed: 12904016
Atanasov BP
Protonation of the beta-lactam nitrogen is the trigger event in the catalytic action of class A beta-lactamases.
Proc Natl Acad Sci U S A 2000 97 3160-3165
PubMed: 10716727
Strynadka NC
Molecular structure of the acyl-enzyme intermediate in beta-lactam hydrolysis at 1.7 A resolution.
Nature 1992 359 700-705
PubMed: 1436034
Chen CC
Structure and kinetics of the beta-lactamase mutants S70A and K73H from Staphylococcus aureus PC1.
Biochemistry 1996 35 12251-12258
PubMed: 8823158
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