A 2-dimensional ratchet model describes assembly initiation of a specialized bacterial cell surface
| Autor: | Jiji Chen, Hari Shroff, Kumaran S. Ramamurthi, Taylor B. Updegrove, Emily A Peluso |
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| Rok vydání: | 2019 |
| Předmět: |
Spores
Bacterial 0303 health sciences Multidisciplinary biology 030306 microbiology Chemistry Cell Membrane Green Fluorescent Proteins Bacillus subtilis biology.organism_classification Septin MreB 03 medical and health sciences Membrane Bacterial Proteins Microscopy Fluorescence PNAS Plus Membrane curvature ATP hydrolysis Biophysics Fluorescence microscope Nuclear lamina 030304 developmental biology |
| Zdroj: | Proceedings of the National Academy of Sciences. 116:21789-21799 |
| ISSN: | 1091-6490 0027-8424 |
| Popis: | Bacterial spores are dormant cells that are encased in a thick protein shell, the “coat,” which participates in protecting the organism’s DNA from environmental insults. The coat is composed of dozens of proteins that assemble in an orchestrated fashion during sporulation. In Bacillus subtilis, 2 proteins initiate coat assembly: SpoVM, which preferentially binds to micron-scale convex membranes and marks the surface of the developing spore as the site for coat assembly; and SpoIVA, a structural protein recruited by SpoVM that uses ATP hydrolysis to drive its irreversible polymerization around the developing spore. Here, we describe the initiation of coat assembly by SpoVM and SpoIVA. Using single-molecule fluorescence microscopy in vivo in sporulating cells and in vitro on synthetic spores, we report that SpoVM’s localization is primarily driven by a lower off-rate on membranes of preferred curvature in the absence of other coat proteins. Recruitment and polymerization of SpoIVA results in the entrapment of SpoVM on the forespore surface. Using experimentally derived reaction parameters, we show that a 2-dimensional ratchet model can describe the interdependent localization dynamics of SpoVM and SpoIVA, wherein SpoVM displays a longer residence time on the forespore surface, which favors recruitment of SpoIVA to that location. Localized SpoIVA polymerization in turn prevents further sampling of other membranes by prelocalized SpoVM molecules. Our model therefore describes the dynamics of structural proteins as they localize and assemble at the correct place and time within a cell to form a supramolecular complex. |
| Databáze: | OpenAIRE |
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