S. pombe Mto1:Mto2 stabilizes γ-tubulin positions within the γ-TuRC
- 1The University of Edinburgh
Abstract
Microtubules are present in all eukaryotes and are nucleated by multiprotein {gamma}-tubulin ring complexes ({gamma}-TuRCs), ring-shaped structures that contain several copies of the {gamma}-tubulin small complex ({gamma}-TuSC). {gamma}-TuRCs nucleate microtubules via a template-based mechanism in which the positions of {gamma}-tubulins in the {gamma}-TuSCs match the position of {gamma}-tubulin dimers in the microtubule lattice. Although {gamma}-TuSC proteins are highly conserved, other components of the {gamma}-TuRC can vary in different organisms, as can their relative importance. Here, we characterize two different simplified {gamma}-TuRCs from fission yeast Schizosaccharomyces pombe, using recombinant purified proteins and negative stain electron microscopy. We show that a nucleation-incompetent {gamma}-TuRC that contains only {gamma}-TuSC proteins plus the microprotein Mzt1 ({gamma}-TuSC:Mzt1) can form rings as efficiently as a large, nucleation-competent complex (MGM) that additionally contains the proteins Mto1 and Mto2. We find that the position of {gamma}-tubulins in {gamma}-TuSC:Mzt1 are less well defined than in MGM. Comparative modelling using our electron microscopy and crosslinking mass spectrometry data, together with structures of {gamma}-TuRCs from other organisms, suggests that Mto1 and Mto2 form a multimeric outer mantle surrounding the {gamma}-TuSC:Mzt1 {gamma}-TuRC. This mantle may stabilize positions of {gamma}-tubulins within MGM, explaining the microtubule-nucleating ability of MGM and highlighting the diversity of non-{gamma}-TuSC proteins in modulating {gamma}-TuRC structure and function.
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BibTeX
@misc{cornu2026pombe,
title = {{S. pombe Mto1:Mto2 stabilizes γ-tubulin positions within the γ-TuRC}},
author = {J. D. Le Cornu and S. L. Leong and E. M. Lynch and H. C. Thakur and K. E. Sawin and A. G. Cook},
howpublished = {bioRxiv},
year = {2026},
month = nov,
doi = {10.64898/2026.11.06.764827},
url = {https://www.biorxiv.org/content/10.64898/2026.11.06.764827v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - S. pombe Mto1:Mto2 stabilizes γ-tubulin positions within the γ-TuRC
AU - J. D. Le Cornu
AU - S. L. Leong
AU - E. M. Lynch
AU - H. C. Thakur
AU - K. E. Sawin
AU - A. G. Cook
PY - 2026
DA - 2026/11/06
PB - bioRxiv
DO - 10.64898/2026.11.06.764827
UR - https://www.biorxiv.org/content/10.64898/2026.11.06.764827v1
AB - Microtubules are present in all eukaryotes and are nucleated by multiprotein {gamma}-tubulin ring complexes ({gamma}-TuRCs), ring-shaped structures that contain several copies of the {gamma}-tubulin small complex ({gamma}-TuSC). {gamma}-TuRCs nucleate microtubules via a template-based mechanism in which the positions of {gamma}-tubulins in the {gamma}-TuSCs match the position of {gamma}-tubulin dimers in the microtubule lattice. Although {gamma}-TuSC proteins are highly conserved, other components of the {gamma}-TuRC can vary in different organisms, as can their relative importance. Here, we characterize two different simplified {gamma}-TuRCs from fission yeast Schizosaccharomyces pombe, using recombinant purified proteins and negative stain electron microscopy. We show that a nucleation-incompetent {gamma}-TuRC that contains only {gamma}-TuSC proteins plus the microprotein Mzt1 ({gamma}-TuSC:Mzt1) can form rings as efficiently as a large, nucleation-competent complex (MGM) that additionally contains the proteins Mto1 and Mto2. We find that the position of {gamma}-tubulins in {gamma}-TuSC:Mzt1 are less well defined than in MGM. Comparative modelling using our electron microscopy and crosslinking mass spectrometry data, together with structures of {gamma}-TuRCs from other organisms, suggests that Mto1 and Mto2 form a multimeric outer mantle surrounding the {gamma}-TuSC:Mzt1 {gamma}-TuRC. This mantle may stabilize positions of {gamma}-tubulins within MGM, explaining the microtubule-nucleating ability of MGM and highlighting the diversity of non-{gamma}-TuSC proteins in modulating {gamma}-TuRC structure and function.
ER -