Crystal structures reveal metal-binding plasticity at the metallo-β-lactamase active site of PqqB from Pseudomonas putida

Xiongying Tu, John A. Latham, Valerie J. Klema, Robert L. Evans, Chao Li, Judith P. Klinman, Carrie M. Wilmot

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


PqqB is an enzyme involved in the biosynthesis of pyrroloquinoline quinone and a distal member of the metallo-β-lactamase (MBL) superfamily. PqqB lacks two residues in the conserved signature motif HxHxDH that makes up the key metal-chelating elements that can bind up to two metal ions at the active site of MBLs and other members of its superfamily. Here, we report crystal structures of PqqB bound to Mn2+, Mg2+, Cu2+, and Zn2+. These structures demonstrate that PqqB can still bind metal ions at the canonical MBL active site. The fact that PqqB can adapt its side chains to chelate a wide spectrum of metal ions with different coordination features on a uniform main chain scaffold demonstrates its metal-binding plasticity. This plasticity may provide insights into the structural basis of promiscuous activities found in ensembles of metal complexes within this superfamily. Furthermore, PqqB belongs to a small subclass of MBLs that contain an additional CxCxxC motif that binds a structural Zn2+. Our data support a key role for this motif in dimerization.

Original languageEnglish (US)
Pages (from-to)1089-1097
Number of pages9
JournalJournal of Biological Inorganic Chemistry
Issue number7
StatePublished - Oct 1 2017

Bibliographical note

Funding Information:
Institutes of Health. The work used Advanced Photon Source beam-lines 19-BM, 19-ID, and GM/CA, the latter funded in whole or in part with Federal funds from the National Cancer Institute (ACB-12002) and the National Institute of General Medical Sciences (AGM-12006). The Advanced Photon Source is a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

Funding Information:
Acknowledgements This research was supported in part by Grants GM-66569 (C.M.W.) and GM-118117 (J.P.K.) from the National

Publisher Copyright:
© 2017, SBIC.


  • Metal-binding plasticity
  • Metallo-β-lactamase
  • PQQ
  • PqqB
  • Pyrroloquinoline quinone
  • X-ray crystallography

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