Institute of Molecular Microbiology and Structural Biochemistry, Lyon
The juxtamembrane domain of StkP is phosphorylated and influences cell division in Streptococcus pneumoniae
doi: 10.1128/mbio.03799-24. Epub ahead of print. PMID: 40197031 Hamidi M, Nagarajan SN, Ravikumar V, Gueguen-Chaignon V, Laguri C, Freton C, Mijakovic I, Simorre J-P, Ravaud S, Grangeasse C.
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Mélisse Hamidi, 26 years old, began her scientific expérience with a Bachelor’s degree in Life Sciences with a focus on Biochemistry and went on to complete a Master’s in Biochemistry and Molecular Biology, specializing in Structural and Functional Biochemistry at Claude Bernard University in Lyon. During her academic career, she developed a strong passion for societal health issues, particularly the critical challenge of antibiotic resistance. Currently, Mélisse is pursuing a PhD with the Pathogenic Bacteria and Protein Phosphorylation team, led by Dr. Christophe Grangeasse at the Institute of Molecular Microbiology and Structural Biochemistry in Lyon. Her doctoral project seeks to unravel the molecular mechanisms that govern cell division in the pathogenic bacterium Streptococcus pneumoniae, aiming to eventually develop new strategies to combat this pathogen. In her research, she focuses on the protein kinase StkP, which orchestrates cell division, and her published work in mBio details the regulatory mechanisms associated with this protein. Looking ahead, Mélisse aspires to undertake postdoctoral research abroad or transition into the biotechnology industry, where she hopes to meet new challenges and further the advancement of scientific research.
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Résumé de l'article
Eukaryotic-like membrane Ser/Thr protein kinases play a pivotal role in different aspects of bacterial physiology. In contrast to the diversity of their extracellular domains, their cytoplasmic catalytic domains are highly conserved. However, the function of a long juxtamembrane domain (JMD), which connects the catalytic domain to the transmembrane helix, remains elusive. In this study, we investigated the function of the JMD of the Ser/Thr protein kinase StkP in the cell division of Streptococcus pneumoniae. We observed that the deletion of the JMD affected the ability of StkP to phosphorylate some of its endogenous substrates, thereby resulting in significant cell morphogenesis defects. Furthermore, multiple threonine residues were identified as being phosphorylated in the JMD.To investigate the functional significance of these phosphorylation sites, we conducted an integrative analysis, combining structural biology, proteomics, and bacterial cell imaging. Our results revealed that the phosphorylation of the JMD did not perturb the phosphorylation of StkP substrates. However, weobserved that it modulated the timing of StkP localization to the division septum and the dynamics of cell constriction. We further demonstrated that phosphorylation of the JMD facilitated the recruitment of several cell division proteins, suggesting that it is required to assemble the division machinery at thedivision septum. In conclusion, this study demonstrates that the function of the JMD of StkP ismodulated by phosphorylation and is critical for the cell division of S. pneumoniae. These observations may serve as a model for understanding the regulatory function of other bacterial Ser/Thr protein kinases.
