title: A dynamically assembled cell wall synthesis machinery buffers cell growth.
abstract: Assembly of protein complexes is a key mechanism for achieving spatial and temporal coordination in processes involving many enzymes. Growth of rod-shaped bacteria is a well-studied example requiring such coordination; expansion of the cell wall is thought to involve coordination of the activity of synthetic enzymes with the cytoskeleton via a stable complex. Here, we use single-molecule tracking to demonstrate that the bacterial actin homolog MreB and the essential cell wall enzyme PBP2 move on timescales orders of magnitude apart, with drastically different characteristic motions. Our observations suggest that PBP2 interacts with the rest of the synthesis machinery through a dynamic cycle of transient association. Consistent with this model, growth is robust to large fluctuations in PBP2 abundance. In contrast to stable complex formation, dynamic association of PBP2 is less dependent on the function of other components of the synthesis machinery, and buffers spatially distributed growth against fluctuations in pathway component concentrations and the presence of defective components. Dynamic association could generally represent an efficient strategy for spatiotemporal coordination of protein activities, especially when excess concentrations of system components are inhibitory to the overall process or deleterious to the cell.
authors.affiliation: Department of Bioengineering and Biophysics Program, Stanford University, Stanford, CA 94305.
authors.forename: Timothy K
authors.initials: TK
authors.lastname: Lee
authors.forename: Carolina
authors.initials: C
authors.lastname: Tropini
authors.forename: Jen
authors.initials: J
authors.lastname: Hsin
authors.forename: Samantha M
authors.initials: SM
authors.lastname: Desmarais
authors.forename: Tristan S
authors.initials: TS
authors.lastname: Ursell
authors.forename: Enhao
authors.initials: E
authors.lastname: Gong
authors.forename: Zemer
authors.initials: Z
authors.lastname: Gitai
authors.forename: Russell D
authors.initials: RD
authors.lastname: Monds
authors.forename: Kerwyn Casey
authors.initials: KC
authors.lastname: Huang
mesh_terms: D002473:Cell Wall / Q000378:metabolism*; D004926:Escherichia coli / Q000254:growth & development*; D029968:Escherichia coli Proteins / Q000378:metabolism; D046915:Penicillin-Binding Proteins / Q000378:metabolism; D059010:Single-Cell Analysis
chemical_list: D029968:Escherichia coli Proteins; D046915:Penicillin-Binding Proteins; C078473:MreB protein, E coli; C582982:MrdA protein, E coli
keywords: Pencillin binding proteins; bacterial cell wall; multienzyme complexes; superresolution microscopy