Assembly and activation of the AAA+ motor of the multi-subunit cobaltochelatase
- 1Department of Biology/Chemistry - Structural Biology of Photosynthetic Microorganisms, University of Osnabrueck, Osnabrueck 49076, Germany
Abstract
Cobalamin is a complex yet essential cobalt-containing cofactor synthesized exclusively by prokaryotes and archaea. Aerobic cobalamin biosynthesis requires the CobNST multi-subunit class I cobaltochelatase for cobalt incorporation. Cobalt chelation is dependent on the energy transfer from the CobST AAA+/VWA motor unit to the substrate-binding catalytic unit (CobN). However, the mechanism for assembly and function of CobNST cobaltochelatase remains poorly understood. Here, we used cryo-EM to solve the structures of the AAA+ motor CobS, in the absence and presence of ATP and its VWA-partner protein CobT. Our data reveal that the AAA+ CobS assembles into various conformations, including hexameric planar rings and different spiral left-handed assemblies: hexamers, double rings and filaments. In the absence of nucleotide, the CobT N-terminal domain interacts with CobS left-handed oligomers, remaining in a half-assembled, nonfunctional motor unit. In the CobST complex, ATP induces conformational rearrangement of CobS from left-handed helical oligomers to a right-handed closed hexamer. The simultaneous repositioning of the CobT VWA domain to the AAA+ central pore shifts the motor unit to a functional state, ready-to-drive CobN-catalyzed chelation reaction. These findings define the mechanism for assembly and activation of the class I cobaltochelatase CobST motor.
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BibTeX
@misc{moura2026assembly,
title = {{Assembly and activation of the AAA+ motor of the multi-subunit cobaltochelatase}},
author = {A. C. Moura and B. Wiseman and E. Bozkurt and E. Deery and R. W. Pickersgill and A. A. Brindley and A. Hitchcock and M. Hoegbom and M. J. Warren and D. Shvarev},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.09.757910},
url = {https://www.biorxiv.org/content/10.64898/2026.10.09.757910v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Assembly and activation of the AAA+ motor of the multi-subunit cobaltochelatase
AU - A. C. Moura
AU - B. Wiseman
AU - E. Bozkurt
AU - E. Deery
AU - R. W. Pickersgill
AU - A. A. Brindley
AU - A. Hitchcock
AU - M. Hoegbom
AU - M. J. Warren
AU - D. Shvarev
PY - 2026
DA - 2026/10/09
PB - bioRxiv
DO - 10.64898/2026.10.09.757910
UR - https://www.biorxiv.org/content/10.64898/2026.10.09.757910v1
AB - Cobalamin is a complex yet essential cobalt-containing cofactor synthesized exclusively by prokaryotes and archaea. Aerobic cobalamin biosynthesis requires the CobNST multi-subunit class I cobaltochelatase for cobalt incorporation. Cobalt chelation is dependent on the energy transfer from the CobST AAA+/VWA motor unit to the substrate-binding catalytic unit (CobN). However, the mechanism for assembly and function of CobNST cobaltochelatase remains poorly understood. Here, we used cryo-EM to solve the structures of the AAA+ motor CobS, in the absence and presence of ATP and its VWA-partner protein CobT. Our data reveal that the AAA+ CobS assembles into various conformations, including hexameric planar rings and different spiral left-handed assemblies: hexamers, double rings and filaments. In the absence of nucleotide, the CobT N-terminal domain interacts with CobS left-handed oligomers, remaining in a half-assembled, nonfunctional motor unit. In the CobST complex, ATP induces conformational rearrangement of CobS from left-handed helical oligomers to a right-handed closed hexamer. The simultaneous repositioning of the CobT VWA domain to the AAA+ central pore shifts the motor unit to a functional state, ready-to-drive CobN-catalyzed chelation reaction. These findings define the mechanism for assembly and activation of the class I cobaltochelatase CobST motor.
ER -