Staphylococcus aureus FtsZ and PBP4 bind to the conformationally dynamic N-terminal domain of GpsB

  1. Michael D. Sacco
  2. Lauren R. Hammond
  3. Radwan E. Noor
  4. Dipanwita Bhattacharya
  5. Jesper J. Madsen
  6. Xiujun Zhang
  7. Shane G. Butler
  8. M. Trent Kemp
  9. Aiden C. Jaskolka-Brown
  10. Sebastian J. Khan
  11. Ioannis Gelis
  12. Prahathees J. Eswara
  13. Yu Chen

  • Curated by eLife

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    This important study reports a unique N-terminal motif of Staphylococcus aureus GpsB and the co-crystal structure of GpsB with the C-terminus of PBP4. It provides convincing evidence demonstrating the interactions of GpsB with PBP4 and FtsZ, shedding light on the role of GpsB in the pathogen's cell division. However, the functional characterization of GpsB's new motif caused and the structural characterization of GpsB and FtsZ's interaction is incomplete.

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Abstract

Bacterial cell division is a tightly regulated process that requires the formation of a dynamic multi-protein complex. In the Firmicutes phylum, GpsB is a membrane associated protein that coordinates peptidoglycan synthesis for cell growth and division. Although GpsB has been studied in several organisms, the structure, function, and interactome of Staphylococcus aureus GpsB is largely uncharacterized, despite being reported as uniquely essential for growth in this clinically relevant bacterium. To address this knowledge gap, we solved the crystal structure of the N-terminal domain of S. aureus GpsB. This structure reveals an atypical asymmetric dimer, and major conformational flexibility that can be mapped to a hinge region formed by a three-residue insertion exclusive to Staphylococci . When this three-residue insertion is excised, its thermal stability increases, and the mutant no longer produces a previously reported lethal phenotype when overexpressed in Bacillus subtilis . Furthermore, we provide the first biochemical, biophysical, and crystallographic evidence that the N-terminal domain of GpsB binds not only PBP4, but also FtsZ, through a conserved recognition motif located on their C-terminus, thus linking peptidoglycan synthesis with cell division. Taken together, the unique structure of S. aureus GpsB and its direct interaction with FtsZ/PBP4 provide deeper insight into the central role of GpsB in S. aureus cell division.

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  1. eLife

    eLife assessment

    This important study reports a unique N-terminal motif of Staphylococcus aureus GpsB and the co-crystal structure of GpsB with the C-terminus of PBP4. It provides convincing evidence demonstrating the interactions of GpsB with PBP4 and FtsZ, shedding light on the role of GpsB in the pathogen's cell division. However, the functional characterization of GpsB's new motif caused and the structural characterization of GpsB and FtsZ's interaction is incomplete.

  2. eLife

    Reviewer #1 (Public Review):

    In the manuscript "Staphylococcus aureus FtsZ and PBP4 bind to the conformationally dynamic N-terminal domain of GpsB", Sacco et. al. solved the crystal structure of S. aureus GpsB, an essential cell growth and division protein. The authors also identified its interactions with the master regulator of cell division FtsZ and a penicillin-binding protein PBP4 that is implicated in B-lactam insensitivity. Although GpsB is essential for growth in S. aureus the reason for its essentiality is poorly understood. The authors used biochemical, biophysical, and crystallographic methods to determine the structure of GpsB and characterized its binding with FtsZ and PBP4. The authors also solved the co-crystal structure of GpsB with the C-terminal peptide of PBP4. These results are significant because it details the interactions of an essential growth protein in S. aureus with known cell division proteins. However, the impact of the work could be further enhanced if the authors had more functional studies to demonstrate the importance of the new hinge motif, the binding with FtsZ C-terminal tail, and PBP4.

  3. eLife

    Reviewer #2 (Public Review):

    This work continues the exploration of the GspB protein as a cytosolic hub for different cell wall enzymes. In particular, this manuscript presents evidence for the direct interaction of GspB with both FtsZ and PBP4 in Staphylococcus aureus. Structural determination is provided for the N-term region of GspB alone and in complex with the small cytosolic region of PBP4 recognized by GspB.

    After previously published works from the same group identifying the connection between GspB and FtsZ, and from another group providing the structural basis for the interaction between GspB and PBPs in different bacterial species; the present work provides incremental information for the S. aureus case. The work is sound, and the experimental evidence supports the presented conclusions.

    The main strength of the manuscript is providing pieces of evidence of the protein-protein interaction between GspB and FtsZ and between GspB and PBP4.

    However, no structural information is provided for the GspB:FtsZ complex, and the 3D structure of the N-term domain of GspB is very similar to previous ones solved for other bacteria, but with the presence of a three-residues insertion that provides flexibility to the domain, a fact that seems to be important in vivo.
    The complex of N-term GspB with the cytosolic micro-domain of PBP4, reveals the interactions involved in the recognition; an interaction network that is similar to the previously reported for GspB and PBPs in bacillus subtilis and in Streptococcus pneumonia.

  4. Version published to 10.1101/2022.10.25.513704v1 on bioRxiv