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Updated: Aug 9, 2026
Genetic Manipulation in Δku80 Strains for Functional Genomic Analysis of Toxoplasma gondii
Published on: July 12, 2013
A photoactivatable crosslinking system reveals protein interactions in the Toxoplasma gondii inner membrane complex
Charles Paul Choi1, Andy Seong Moon2, Peter Sungmin Back1
1Molecular Biology Institute, University of California, Los Angeles, Los Angeles, California, United States of America.
Insights
This study introduces a novel method using unnatural amino acids to map protein interactions within the Toxoplasma gondii inner membrane complex (IMC). The findings reveal new details about the IMC
Area of Science:
- Parasitology
- Cell Biology
- Structural Biology
Background:
- The Toxoplasma gondii inner membrane complex (IMC) is crucial for parasite motility and replication.
- Understanding protein interactions within the IMC cytoskeletal network is vital but challenging due to the sensitivity of protein complexes.
- Current knowledge of IMC protein associations is limited.
Purpose of the Study:
- To develop and apply a novel photoreactive unnatural amino acid (UAA) crosslinking system for studying protein-protein interactions in the native intracellular environment of T. gondii.
- To investigate the protein interactions of the essential IMC protein ILP1.
- To gain insights into the architectural organization of the apicomplexan IMC cytoskeleton.
Main Methods:
- Application of a photoreactive unnatural amino acid (UAA) crosslinking system.
- In vivo crosslinking to capture protein interactions within the native parasite.
- Analysis of crosslinked products to identify interacting partners and binding interfaces.
Main Results:
- The UAA crosslinking system successfully captured protein interactions within the IMC.
- Distinct regions of the ILP1 C-terminal coiled-coil domain were shown to crosslink with IMC3, IMC6, and IMC27.
- The IMC3 C-terminal domain and IMC6 N-terminal domain were identified as necessary for binding to ILP1.
Conclusions:
- A new method for studying protein-protein interactions in Toxoplasma was established.
- The study provides the first insights into the architecture of the IMC cytoskeletal network.
- Specific interactions between ILP1 and other IMC components (IMC3, IMC6, IMC27) were elucidated.
Abstract:
The Toxoplasma gondii inner membrane complex (IMC) is an important organelle involved in parasite motility and replication. The IMC resides beneath the parasite's plasma membrane and is composed of both membrane and cytoskeletal components. Although the protein composition of the IMC is becoming better understood, the protein-protein associations that enable proper functioning of the organelle remain largely unknown. Determining protein interactions in the IMC cytoskeletal network is particularly challenging, as disrupting the cytoskeleton requires conditions that disrupt protein complexes. To circumvent this problem, we demonstrate the application of a photoreactive unnatural amino acid (UAA) crosslinking system to capture protein interactions in the native intracellular environment. In addition to identifying binding partners, the UAA approach maps the binding interface of the bait protein used for crosslinking, providing structural information of the interacting proteins. We apply this technology to the essential IMC protein ILP1 and demonstrate that distinct regions of its C-terminal coiled-coil domain crosslink to the alveolins IMC3 and IMC6, as well as IMC27. We also show that the IMC3 C-terminal domain and the IMC6 N-terminal domain are necessary for binding to ILP1, further mapping interactions between ILP1 and the cytoskeleton. Together, this study develops a new approach to study protein-protein interactions in Toxoplasma and provides the first insight into the architecture of the cytoskeletal network of the apicomplexan IMC.
