# Structural Studies of the Coronavirus Life Cycle

> **NIH NIH R00** · UNIVERSITY OF WISCONSIN-MADISON · 2021 · $248,994

## Abstract

SUMMARY
 Coronaviruses are sporadically emerging viruses responsible for SARS and MERS disease
outbreaks. There are currently no direct treatments for these viruses, nor is there a vaccine which
induces broad protection from infection. However, several stages in the virus life cycle are promising
targets for therapeutic intervention. Cell entry is mediated by the large glycoprotein spike, which binds
to host receptors and mediates fusion of the viral and host membranes. The ability of coronaviruses to
adapt to new species or escape from the immune system is attributed to the viral spike protein. Once
inside the cell, the viral RNA synthesis complex is assembled from 16 non-structural proteins (NSP)
which transcribe, edit and modify viral RNAs and remodel ER membranes to create RNA replication
factories. Expression of the viral structural proteins involves the RNA synthesis complex carrying out
discontinuous strand synthesis to produce a nested set of viral mRNAs with truncations of the 5' open
reading frames. Discontinuous strand synthesis is essential for the production of new virions and
understanding its mechanisms will shed light on related viral processes such as viral recombination to
generate spike variants with altered serotypes or host tropisms.
 During the K99 phase, I will obtain training in cryo-electron microscopy to complement my
expertise in X-ray crystallography. I will use cryo-electron microscopy to examine the distinct
conformations of the coronavirus spike protein as it binds host receptors and is primed for the fusion
process by host proteases as I transition to the R00 phase of the award. These studies build on the
recent structure determination of the HKU1-CoV spike protein from Dr. Andrew Ward's laboratory to
which I contributed. Not only does this spike structure demonstrate the feasibility of the proposed
experiments, but also provides a basis for new hypotheses of spike protein function.
 Also during the K99 phase, I will utilize the expertise of Dr. Erica Saphire's laboratory to
develop RNA helicase assays to assess the function of the viral NSP13 helicase. I will use these
assays to provide mechanistic, biochemical evidence to identify RNA templates upon which the
NSP13 helicase stalls and may lead to induction of the RNA synthesis complex to carryout
discontinuous strand synthesis. During the R00 phase, I will complement these studies with
biochemistry, X-ray crystallography and cryo-electron microscopy to identify molecular mechanisms
by which NSP13 recognizes RNA substrates and communicates with the RNA synthesis complex.
These proposed studies will illuminate novel targets for antiviral therapy.

## Key facts

- **NIH application ID:** 10074514
- **Project number:** 5R00AI123498-04
- **Recipient organization:** UNIVERSITY OF WISCONSIN-MADISON
- **Principal Investigator:** Robert N Kirchdoerfer
- **Activity code:** R00 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $248,994
- **Award type:** 5
- **Project period:** 2017-07-14 → 2022-11-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10074514

## Citation

> US National Institutes of Health, RePORTER application 10074514, Structural Studies of the Coronavirus Life Cycle (5R00AI123498-04). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10074514. Licensed CC0.

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