Structure of beta-lactam synthetase reveals how to synthesize antibiotics instead of asparagine

Nat Struct Biol. 2001 Aug;8(8):684-9. doi: 10.1038/90394.


The enzyme beta-lactam synthetase (beta-LS) catalyzes the formation of the beta-lactam ring in clavulanic acid, a clinically important beta-lactamase inhibitor. Whereas the penicillin beta-lactam ring is generated by isopenicillin N synthase (IPNS) in the presence of ferrous ion and dioxygen, beta-LS uses ATP and Mg2+ as cofactors. According to sequence alignments, beta-LS is homologous to class B asparagine synthetases (AS-Bs), ATP/Mg2+-dependent enzymes that convert aspartic acid to asparagine. Here we report the first crystal structure of a beta-LS. The 1.95 A resolution structure of Streptomyces clavuligerus beta-LS provides a fully resolved view of the active site in which substrate, closely related ATP analog alpha,beta-methyleneadenosine 5'-triphosphate (AMP-CPP) and a single Mg2+ ion are present. A high degree of substrate preorganization is observed. Comparison to Escherichia coli AS-B reveals the evolutionary changes that have taken place in beta-LS that impede interdomain reaction, which is essential in AS-B, and that accommodate beta-lactam formation. The structural data provide the opportunity to alter the synthetic potential of beta-LS, perhaps leading to the creation of new beta-lactamase inhibitors and beta-lactam antibiotics.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphate / analogs & derivatives
  • Adenosine Triphosphate / metabolism
  • Amidohydrolases / antagonists & inhibitors
  • Amidohydrolases / chemistry*
  • Amidohydrolases / metabolism*
  • Amino Acid Sequence
  • Anti-Bacterial Agents / biosynthesis*
  • Asparagine / metabolism*
  • Aspartate-Ammonia Ligase / chemistry
  • Aspartate-Ammonia Ligase / classification
  • Binding Sites
  • Clavulanic Acid / chemistry
  • Clavulanic Acid / metabolism
  • Crystallography, X-Ray
  • Escherichia coli / enzymology
  • Evolution, Molecular
  • Magnesium / metabolism
  • Models, Molecular
  • Molecular Sequence Data
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Sequence Alignment
  • Streptomyces / enzymology*
  • Structure-Activity Relationship


  • Anti-Bacterial Agents
  • Clavulanic Acid
  • Asparagine
  • Adenosine Triphosphate
  • Amidohydrolases
  • beta-lactam synthetase
  • Aspartate-Ammonia Ligase
  • Magnesium
  • alpha,beta-methyleneadenosine 5'-triphosphate

Associated data

  • PDB/1JGT