Cryo-electron tomography sheds light on the largest protein in the Trypanosoma brucei tripartite attachment complex
Year: 2026
Type: preprint
Abstract: Trypanosomes only contain a single mitochondrion per cell. Within that singular mitochondrion, the protist carries a single mitochondrial genome that consists of a complex DNA network, the kinetoplast DNA (kDNA). The replicated kDNA is segregated during cell division by the tripartite attachment complex (TAC), a multi-protein bridge that physically links each daughter kDNA to a basal body (BB). BB movements drive kDNA segregation prior to cell division. How the TAC accommodates constant BB movements while maintaining a stable kDNA anchor throughout the cell cycle has remained unclear. Here we used cryo-electron tomography to image the cytoplasmic part of the TAC in its native context. We resolved the BB, the mitochondrial membranes, and the exclusion zone filaments (EZFs) connecting the BB and pro-BB to the outer mitochondrial membrane (OMM) and quantified the geometry of the region across many cells. EZF lengths spanned 230 to 625 nm in zoid cells and up to 874 nm in NP40-treated cells, and the BB occupied a wide range of positions and orientations relative to the OMM, while the pro-BB sat closer and more constrained. Building on these observations and prior evidence that p197 alone defines the BB-OMM distance, we propose that p197 is a length-variable connector: the length of a tandem array of α-helical repeats depends on their relative orientation, and filaments of different lengths coexist at one basal body. How that orientation is set remains open, but such a connector reconciles stable kDNA anchoring with the mechanical demands of BB movement during the cell cycle.
Source: eLife
Language: English
Subfield: Epidemiology
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $2,500
Funders: Universität Basel, University of Bern, Wellcome Trust, Diamond Light Source, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Eidgenössische Technische Hochschule Zürich, Uniscientia Foundation, Medical Research Council, Biotechnology and Biological Sciences Research Council
OpenAlex ID: W7225196902