4S-fluorination of ProB29 in insulin lispro slows fibril formation

Stephanie L. Breunig, Alex M. Chapman, Jeanne LeBon, Janine C. Quijano, Maduni Ranasinghe, Jeffrey Rawson, Borries Demeler, Hsun Teresa Ku, David A. Tirrell

Research output: Contribution to journalArticlepeer-review


Recombinant insulin is a life-saving therapeutic for millions of patients affected by diabetes mellitus. Standard mutagenesis has led to insulin variants with improved control of blood glucose; for instance, the fast-acting insulin lispro contains two point mutations that suppress dimer formation and expedite absorption. However, insulins undergo irreversible denaturation, a process accelerated for the insulin monomer. Here we replace ProB29 of insulin lispro with 4R-fluoroproline, 4S-fluoroproline, and 4,4-difluoroproline. All three fluorinated lispro variants reduce blood glucose in diabetic mice, exhibit similar secondary structure as measured by CD, and rapidly dissociate from the zinc- and resorcinol-bound hexamer upon dilution. Notably, however, we find that 4S-fluorination of ProB29 delays the formation of undesired insulin fibrils that can accumulate at the injection site in vivo and can complicate insulin production and storage. These results demonstrate how subtle molecular changes achieved through non-canonical amino acid mutagenesis can improve the stability of protein therapeutics.

Original languageEnglish
Article number107332
Pages (from-to)107332
JournalJournal of Biological Chemistry
Issue number6
StatePublished - Jun 2024


  • fibrillation
  • fluoroproline
  • insulin
  • insulin lispro
  • non-canonical amino acid
  • proline


Dive into the research topics of '4S-fluorination of ProB29 in insulin lispro slows fibril formation'. Together they form a unique fingerprint.

Cite this