# Structure and function of the Plasmodium myosin XIV-actin glideosome.

> **NIH NIH R01** · UNIVERSITY OF VERMONT & ST AGRIC COLLEGE · 2024 · $661,630

## Abstract

Malaria infection in humans, caused by single-celled parasites from the genus Plasmodium, is a major global
health challenge. Despite marked progress in the last 15 years, more than 400 million deaths occur worldwide
annually, the majority being children under age 5. Recent licensure of the first ever malaria vaccine heralds a
new era in efforts to control malaria, but the relatively modest efficacy of the RTS,S vaccine means that
complementary approaches will be essential if the WHO's goal of a 90% reduction in rates by 2030 is to be
realized. Malaria parasites are motile throughout their complex human and mosquito lifecycle. They move by a
process called gliding motility, which underpins their ability to reach, cross, and enter host tissues and cells.
Gliding is powered by a parasite actomyosin motor the disruption of which kills the infectious parasite. Towards
development of the parasite actomyosin motor as a druggable target, our collaborative team has worked to
characterize the essential class XIV single-headed myosin motor PfMyoA, the core of gliding motility. We were
the first to characterize and crystallize PfMyoA, demonstrating that its function is uniquely tuned by N-terminal
heavy chain phosphorylation. We were the first to show the essential role of PfMyoA and its essential light chain
in powering red blood cell (RBC) invasion, the stage responsible for all malaria pathogenesis. We have since
used PfMyoA mutants to reveal the energetic barriers necessary for RBC invasion using live cell imaging. These
foundations expertly position our team to extend investigation of gliding motility across the malaria lifecycle and
explore additional Plasmodium myosins and their cellular roles, which are the combined aims of this competitive
renewal. We propose (Aim 1) to define the cellular roles of PfMyoB versus PfMyoA by comparing structures,
functional properties, and the role of heavy chain phosphorylation in vitro and in vivo. Aim 2 proposes to
determine the binding pocket, mechanism of action, and impact on the parasite of two first-in-class small
molecule inhibitors of PfMyoA ATPase activity. Aim 3 investigates two other essential Plasmodium myosins
(PfMyoF and K), which are virtually unstudied both as motors and potential future druggable targets. PfMyoF
likely plays a role as a processive transporter, while PfMyoK likely functions during sexual development, with
motor domain inserts typical of reverse-directionality in eukaryotic class VI motors. We will use an integrative
approach highlighting in vitro functional assays (motility and ensemble force assays, optical trap assays, steady-
state and transient kinetics) and structural studies (X-ray crystallography and cryo-EM) together with live cell
approaches (including super resolution imaging) and genetic investigation of motors (conditional
knockouts/substitutions) in several stages of the Plasmodium parasite lifecycle. At completion we will have
developed a previously unattainable depth o...

## Key facts

- **NIH application ID:** 10873178
- **Project number:** 5R01AI132378-08
- **Recipient organization:** UNIVERSITY OF VERMONT & ST AGRIC COLLEGE
- **Principal Investigator:** KATHLEEN M TRYBUS
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $661,630
- **Award type:** 5
- **Project period:** 2017-05-11 → 2027-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10873178

## Citation

> US National Institutes of Health, RePORTER application 10873178, Structure and function of the Plasmodium myosin XIV-actin glideosome. (5R01AI132378-08). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10873178. Licensed CC0.

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