Surprising structure of Toxoplasma gondii GAC
After years of work, we finally can see what the apicomplexan glideosome-associated connector (GAC) really looks like! Check out our latest preprint presenting the structure in two drastically different conformations. Based on its structure, we suggest a role for GAC as an elastic spring helping parasite motility and invasion.
The apicompelxan glideosome-associated connector (GAC) is a giant armadillo-repeat protein, which is essential for parasite motility and host cell invasion and conserved across the phylum. GAC connects actin filaments to the plasma membrane via interactions with phosphatidic acid and membrane-spanning adhesins. We determined the crystal structure of full-length Toxoplasma gondii GAC at 2.3 Å resolution and explored its conformational space in solution using SAXS and cryo-EM. The crystal structure reveals a surprising compact conformation but we show that, in solution, GAC adopts both compact and extended forms. The PH domain stabilizes the compact form seen in the crystal and may act as a switch triggered by membrane sensing. Based on its spring-like architecture, we suggest a role for GAC as an elastic element in actomyosin force generation during apicomplexan parasite gliding motility and invasion.