Localization and single molecule dynamics of Bacillus subtilis penicillin-binding proteins depend on substrate availability and are affected by stress conditions
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Publisher
MDPI
Abstract
We have used single molecule tracking to investigate dynamics of four penicillinbinding proteins (PBPs) in Bacillus subtilis to shed light on their possible modes of action.
We show that Pbp2a, Pbp3, Pbp4, and Pbp4a, when expressed at very low levels, show at
least two distinct states of mobility: a state of slow motion, likely representing molecules
involved in cell wall synthesis, and a mode of fast motion, likely representing freely
diffusing molecules. Except for Pbp4, all other PBPs showed about 50% molecules in the
slow mobility state, suggesting that roughly half of all molecules are engaged in a substratebound mode. We observed similar coefficients for the slow mobility state for Pbp4 and
Pbp4a on the one hand, and for Pbp2a and Pbp3 on the other hand, indicating possible joint
activities, respectively. Upon induction of osmotic stress, Pbp2a and Pbp4a changed from
a pattern of localization mostly at the lateral cell membrane to also include localization
at the septum, revealing that sites of preferred positioning for these two PBPs can be
modified during stress conditions. While Pbp3 became more dynamic after induction of
osmotic stress, Pbp4 became more static, showing that PBPs reacted markedly differently to
envelope stress conditions. The data suggest that PBPs could take over functions in cell wall
synthesis during different stress conditions, increasing the resilience of cell wall homeostasis
in different environmental conditions. All PBPs lost their respective localization pattern
after the addition of vancomycin or penicillin G, indicating that patterns largely depend
on substrate availability. Our findings show that PBPs rapidly alter between non-targeted
motion through the cell membrane and capture at sites of active cell wall synthesis, most
likely guided by complex formation with other cell wall synthesis enzymes.
Metadata
Philipps-Universität Marburg
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Except where otherwised noted, this item's license is described as Attribution 4.0 International