# Biosynthesis of Beta Lactam Antibiotics

> **NIH NIH R01** · JOHNS HOPKINS UNIVERSITY · 2022 · $629,710

## Abstract

Project Summary/Abstract
The biosynthesis of three of the four “non-classical” clans of the b-lactam antibiotics will be investigated.
Together with the fifth, or “classical” penicillins and cephalosporins, these drugs constitute >60% of the world
antibiotic market and account for >$25B/yr in economic value. They remain vital mainstays of human health
and longevity, but with their widespread use has come the inevitable rise of antibiotic-resistant infections.
Structural modifications have slowed these effects, but there is increased reliance on the newer, non-classical
families; for example, the b-lactamase inhibitor clavulanic acid and the potent, broad-spectrum carbapenems
like Imipenem® and Meropenem,® inspired by the natural product thienamycin. The b-lactams are instructive
examples of convergent evolution where the pathways to the five known classes exemplify remarkably
different biosynthetic strategies, evolution of enzyme function to new tasks and impressive synthetic
efficiency. In each of the three pathways to be investigated, remarkable, often unprecedented reactions, take
place that will be studied using tools ranging from organic synthesis to enzymology, protein X-ray
crystallography and in silico modeling to understand their enzyme mechanisms. This knowledge will be used
to explore their potential for functional reprogramming and targeted mutation for the chemo-enzymatic
synthesis of antibiotic variants of practical value. Much is known about structure/activity relationships among
these drugs where manufacturing costs might be reduced by fermentation technology based on engineered
biosynthetic enzymes and semi-synthesis. The enzymes of interest range from three cobalamin-dependent
radical S-adenosylmethionine enzymes that we know now lie at the heart of carbapenem biosynthesis, to
evolved domains of larger non-ribosomal peptide synthetases (NRPSs) that create b-lactam rings from peptide
precursors in two strikingly distinct ways. One leads from a peptide seryl residue to the internal 4-membered
ring of monocyclic b-lactam antibiotics while the other gives monobactams directly with their distinctive N-
sulfonated b-lactam rings fully fledged. Renewed clinical interest attaches to this structural class for its
clinically important property of resistance to Class B, or Zn++ metallo-b-lactamases, which can overmatch even
the most potent carbapenems. We have recently shown the synthesis of the monobactam core is carried out in
the C-terminal thioesterase (TE) domain of a NRPS. We have a crystal structure of this domain with a substrate
mimic bound. Proposed are experiments to remodel the active site to accommodate stereoisomers of the native
substrate to synthesize differently substituted monobactams. A combination of biochemical experiments,
chemical crosslinking and x-ray crystallography will guide the engineering of a small library of TE domains
for possible immobilization and the application of flow technology for larger scale synthe...

## Key facts

- **NIH application ID:** 10406371
- **Project number:** 5R01AI121072-07
- **Recipient organization:** JOHNS HOPKINS UNIVERSITY
- **Principal Investigator:** CRAIG ARTHUR TOWNSEND
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $629,710
- **Award type:** 5
- **Project period:** 2016-02-01 → 2025-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10406371

## Citation

> US National Institutes of Health, RePORTER application 10406371, Biosynthesis of Beta Lactam Antibiotics (5R01AI121072-07). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10406371. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*