Samantha Desmarais - A dynamically assembled cell-wall synthesis machinery buffers cell growth

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      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.

        February 18, 2014, PNAS,   doi:10.1073/pnas.1324044111.

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