Recovery of a minor cryo-EM particle population reveals conformational equilibria linking cofactor loading, turnover, and reactivation in methionine synthase
- 1Cornell University
Abstract
Cobalamin-dependent methionine synthase (MetH) is a highly dynamic enzyme that requires large-scale domain rearrangements to facilitate turnover and reactivation. Despite significant biochemical and structural efforts, a full picture of the conformational changes underlying the transition between MetH turnover and reactivation has remained elusive. Here, we leverage state-of-the-art cryo-electron microscopy (cryo-EM) methods to reanalyze an old dataset and gain new insights into these changes. By utilizing a neural-network particle picker, performing careful classification of particles, and incorporating high-resolution information to determine initial particle orientations, we uncovered and reconstructed a minor population of reactivation-state MetH (~4.5-5 [A] resolution) from a dataset that is dominated by resting-state MetH. This structure represents the first fully intact structure of the enzyme with a physiological cobalamin cofactor bound. These findings highlight the potential for improved cryo-EM methodology to uncover previously hidden details about enzyme function and deepen our understanding of structural ensembles.
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BibTeX
@misc{wang2026recovery,
title = {{Recovery of a minor cryo-EM particle population reveals conformational equilibria linking cofactor loading, turnover, and reactivation in methionine synthase}},
author = {H. Wang and M. B. Watkins and P. Suksmith and N. Ando},
howpublished = {bioRxiv},
year = {2026},
month = jul,
doi = {10.64898/2026.07.27.741092},
url = {https://www.biorxiv.org/content/10.64898/2026.07.27.741092v2},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Recovery of a minor cryo-EM particle population reveals conformational equilibria linking cofactor loading, turnover, and reactivation in methionine synthase
AU - H. Wang
AU - M. B. Watkins
AU - P. Suksmith
AU - N. Ando
PY - 2026
DA - 2026/07/27
PB - bioRxiv
DO - 10.64898/2026.07.27.741092
UR - https://www.biorxiv.org/content/10.64898/2026.07.27.741092v2
AB - Cobalamin-dependent methionine synthase (MetH) is a highly dynamic enzyme that requires large-scale domain rearrangements to facilitate turnover and reactivation. Despite significant biochemical and structural efforts, a full picture of the conformational changes underlying the transition between MetH turnover and reactivation has remained elusive. Here, we leverage state-of-the-art cryo-electron microscopy (cryo-EM) methods to reanalyze an old dataset and gain new insights into these changes. By utilizing a neural-network particle picker, performing careful classification of particles, and incorporating high-resolution information to determine initial particle orientations, we uncovered and reconstructed a minor population of reactivation-state MetH (~4.5-5 [A] resolution) from a dataset that is dominated by resting-state MetH. This structure represents the first fully intact structure of the enzyme with a physiological cobalamin cofactor bound. These findings highlight the potential for improved cryo-EM methodology to uncover previously hidden details about enzyme function and deepen our understanding of structural ensembles.
ER -