Biocatalytic control of site-selectivity and chain length-selectivity in radical amino acid halogenases

Elijah N. Kissman, Monica E. Neugebauer, Kiera H. Sumida, Cameron V. Swenson, Nicholas A. Sambold, Jorge A. Marchand, Douglas C. Millar, Michelle C.Y. Chang

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Biocatalytic C–H activation has the potential to merge enzymatic and synthetic strategies for bond formation. FeII/αKG-dependent halogenases are particularly distinguished for their ability both to control selective C–H activation as well as to direct group transfer of a bound anion along a reaction axis separate from oxygen rebound, enabling the development of new transformations. In this context, we elucidate the basis for the selectivity of enzymes that perform selective halogenation to yield 4-Cl-lysine (BesD), 5-Cl-lysine (HalB), and 4-Cl-ornithine (HalD), allowing us to probe how site-selectivity and chain length selectivity are achieved. We now report the crystal structure of the HalB and HalD, revealing the key role of the substrate-binding lid in positioning the substrate for C4 vs C5 chlorination and recognition of lysine vs ornithine. Targeted engineering of the substrate-binding lid further demonstrates that these selectivities can be altered or switched, showcasing the potential to develop halogenases for biocatalytic applications.

Original languageEnglish (US)
Article numbere2214512120
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number12
StatePublished - Mar 21 2023
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General


  • biocatalysis
  • bioinorganic chemistry
  • C-H activation
  • enzymology
  • structural biology


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