GpsB Coordinates StkP Signaling as a PASTA Kinase Adaptor in Streptococcus pneumoniae Cell Division

Area of Science:

• Microbiology
• Cell Biology
• Biochemistry

Background:

• StkP is a Ser/Thr protein kinase in Streptococcus pneumoniae that regulates growth and division by sensing cell wall signals.
• GpsB is a cell division protein essential for septal ring formation and closure, influencing StkP activity.

Purpose of the Study:

• To investigate the interaction between StkP and GpsB and its impact on StkP kinase activity and substrate phosphorylation.
• To elucidate the role of GpsB phosphorylation in modulating StkP function and bacterial cell division.

Main Methods:

• Phosphoproteomic analysis to identify GpsB phosphorylation sites.
• In vitro and in vivo kinase assays to assess StkP and GpsB phosphorylation.
• Bacterial two-hybrid assays and co-immunoprecipitation to study protein interactions.
• Site-directed mutagenesis of GpsB phosphorylation sites.

Main Results:

• GpsB significantly enhances StkP autophosphorylation and substrate phosphorylation.
• StkP directly phosphorylates GpsB at T79 and T83 residues.
• GpsB phosphorylation modulates its interaction with StkP, affecting StkP activity and cell division.
• Mutations in GpsB phosphorylation sites impair StkP-dependent phosphorylation and cell division.

Conclusions:

• GpsB acts as an adaptor protein that promotes StkP activity by facilitating its recruitment and substrate specificity.
• Dynamic phosphorylation and dephosphorylation of GpsB regulate StkP kinase activity during bacterial growth and stress.
• This signaling pathway is critical for maintaining the proper functioning of Streptococcus pneumoniae.