TY - JOUR
T1 - AimB Is a Small Protein Regulator of Cell Size and MreB Assembly
AU - Werner, John N.
AU - Shi, Handuo
AU - Hsin, Jen
AU - Huang, Kerwyn Casey
AU - Gitai, Zemer
AU - Klein, Eric A.
N1 - Funding Information:
We thank Anna Konovalova (Health Science Center, The University of Texas, Houston, TX) for helpful discussions and assistance with the photo-cross-linking assay and Christine Jacobs-Wager (Yale University, New Haven, CT) for providing CRISPRi reagents. Funding was provided by National Science Foundation CAREER Award MCB-1149328, the Stanford University Center for Cancer Systems Biology under grant P50-GM107615, and the Allen Discovery Center at Stanford University on Systems Modeling of Infection (to K.C.H.); National Institutes of Health Ruth L. Kirschstein National Research Service Award 1F32GM100677 (to J.H.); an Agilent Fellowship, a Stanford Interdisciplinary Graduate Fellowship, and a James McDonnell Postdoctoral Fellowship (to H.S.); National Institutes of Health grant R01GM107384 (to Z.G.); and National Science Foundation CAREER Award MCB-1553004 (to E.A.K.). K.C.H. is a Chan Zuckerberg Investigator. All simulations were performed with computer time provided by the Extreme Science and Engineering Discovery Environment, which is supported by National Science Foundation grant OCI-1053575, with allocation number TG-MCB110056 (to K.C.H.).
Funding Information:
Funding was provided by National Science Foundation CAREER Award MCB-1149328 , the Stanford University Center for Cancer Systems Biology under grant P50-GM107615 , and the Allen Discovery Center at Stanford University on Systems Modeling of Infection (to K.C.H.); National Institutes of Health Ruth L. Kirschstein National Research Service Award 1F32GM100677 (to J.H.); an Agilent Fellowship, a Stanford Interdisciplinary Graduate Fellowship, and a James McDonnell Postdoctoral Fellowship (to H.S.); National Institutes of Health grant R01GM107384 (to Z.G.); and National Science Foundation CAREER Award MCB-1553004 (to E.A.K.). K.C.H. is a Chan Zuckerberg Investigator. All simulations were performed with computer time provided by the Extreme Science and Engineering Discovery Environment, which is supported by National Science Foundation grant OCI-1053575 , with allocation number TG-MCB110056 (to K.C.H.).
Publisher Copyright:
© 2020 Biophysical Society
PY - 2020/8/4
Y1 - 2020/8/4
N2 - The MreB actin-like cytoskeleton assembles into dynamic polymers that coordinate cell shape in many bacteria. In contrast to most other cytoskeleton systems, few MreB-interacting proteins have been well characterized. Here, we identify a small protein from Caulobacter crescentus, an assembly inhibitor of MreB (AimB). AimB overexpression mimics inhibition of MreB polymerization, leading to increased cell width and MreB delocalization. Furthermore, aimB appears to be essential, and its depletion results in decreased cell width and increased resistance to A22, a small-molecule inhibitor of MreB assembly. Molecular dynamics simulations suggest that AimB binds MreB at its monomer-monomer protofilament interaction cleft and that this interaction is favored for C. crescentus MreB over Escherichia coli MreB because of a closer match in the degree of opening with AimB size, suggesting coevolution of AimB with MreB conformational dynamics in C. crescentus. We support this model through functional analysis of point mutants in both AimB and MreB, photo-cross-linking studies with site-specific unnatural amino acids, and species-specific activity of AimB. Together, our findings are consistent with AimB promoting MreB dynamics by inhibiting monomer-monomer assembly interactions, representing a new mechanism for regulating actin-like polymers and the first identification of a non-toxin MreB assembly inhibitor. Because AimB has only 104 amino acids and small proteins are often poorly characterized, our work suggests the possibility of more bacterial cytoskeletal regulators to be found in this class. Thus, like FtsZ and eukaryotic actin, MreB may have a rich repertoire of regulators to tune its precise assembly and dynamics.
AB - The MreB actin-like cytoskeleton assembles into dynamic polymers that coordinate cell shape in many bacteria. In contrast to most other cytoskeleton systems, few MreB-interacting proteins have been well characterized. Here, we identify a small protein from Caulobacter crescentus, an assembly inhibitor of MreB (AimB). AimB overexpression mimics inhibition of MreB polymerization, leading to increased cell width and MreB delocalization. Furthermore, aimB appears to be essential, and its depletion results in decreased cell width and increased resistance to A22, a small-molecule inhibitor of MreB assembly. Molecular dynamics simulations suggest that AimB binds MreB at its monomer-monomer protofilament interaction cleft and that this interaction is favored for C. crescentus MreB over Escherichia coli MreB because of a closer match in the degree of opening with AimB size, suggesting coevolution of AimB with MreB conformational dynamics in C. crescentus. We support this model through functional analysis of point mutants in both AimB and MreB, photo-cross-linking studies with site-specific unnatural amino acids, and species-specific activity of AimB. Together, our findings are consistent with AimB promoting MreB dynamics by inhibiting monomer-monomer assembly interactions, representing a new mechanism for regulating actin-like polymers and the first identification of a non-toxin MreB assembly inhibitor. Because AimB has only 104 amino acids and small proteins are often poorly characterized, our work suggests the possibility of more bacterial cytoskeletal regulators to be found in this class. Thus, like FtsZ and eukaryotic actin, MreB may have a rich repertoire of regulators to tune its precise assembly and dynamics.
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U2 - 10.1016/j.bpj.2020.04.029
DO - 10.1016/j.bpj.2020.04.029
M3 - Article
C2 - 32416080
AN - SCOPUS:85084592239
SN - 0006-3495
VL - 119
SP - 593
EP - 604
JO - Biophysical Journal
JF - Biophysical Journal
IS - 3
ER -