Molecular coordination of cell shape determinants in Helicobacter pylori: Insights into the dynamics and spatial organization of peptidoglycan-modifying complexes
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Philipps-Universität Marburg
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Abstract
The helical morphology characteristic of the widespread human pathogenic organism Helicobacter pylori enables efficient colonization of the epithelial cells of the stomach and makes diseases such as gastric ulcers or gastric cancer more likely. The formation and maintenance of the helical cell shape of H. pylori is the result of the interaction of several proteins, some of which act independently of each other. One group of these proteins comprises the so-called cell shape determinant (Csd) proteins, which, together with the bactofilin CcmA, influence the cell shape by locally defined changes in the structure of the cell shape-determining peptidoglycan. Despite numerous studies that have focused on the identification of these proteins and their interaction with each other through in vitro experiments, little is known about their subcellular localization and dynamics in living cells. Furthermore, the role of the bactofilin CcmA within the complex is not fully understood.
The present work deals with the DD-endopeptidases Csd1 and Csd2, the transmembrane protein Csd7 as a representative of the cell shape-defining proteins, as well as the bactofilin CcmA in H. pylori. This provides the first insight into the organization and dynamics of endopeptidases and their interactors. The knowledge gained enables a refinement of the previously known understanding of how active PG modifications are brought about by the interaction of endopeptidases and other associated factors.
Using a combination of high-resolution structured illumination microscopy and cluster tracking, regions close to the cell poles were defined as areas with the most restricted diffusion of Csd2 and thus its highest activity. Furthermore, a ring-like structure with a global Csd2-Minimum could be identified at these regions, which showed a rotation-like movement. However, this preferred Csd1:Csd2 localization showed only a slight overlap with PG-growing zones at the septum. This implies a specialized function of the endopeptidase that focuses on PG modification rather than PG expansion. The organization of regions close to the cell poles seems to indicate a locally increased enzymatic activity. In addition, the Csd1:Csd2:Csd7 complex showed an independent movement pattern in contrast to other Cell-shape regulating components like Csd5 or CcmA.
The transmembrane protein Csd7 has a stabilizing effect on the Csd1:Csd2 heterodimer, but shows an independent organization in a helical arrangement across the cell length. While static Csd2 occurs preferentially in regions close to the cell pole, static Csd7 exhibits a more widely distributed diffusion behavior. While SMT experiments excluded an effect on the diffusion of Csd7 by CcmA, a spatial proximity to the bactofilin could be observed by bimolecular fluorescence complementation (BiFC). However, this supports the assumption of independence of Csd7 from Csd2, Csd1, and CcmA.
Although CcmA showed no direct interaction affinity to the Csd1:Csd2:Csd7 complex, it still has a significant influence on the helical cell shape of H. pylori. CcmA showed a slight tendency towards
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positive curvature only in the polymerized and thus functional state. The potential interaction partner MinD identified by Co-immunoprecipitation, which is part of the septum-defining system, has a major influence on the diffusion behavior of CcmA. In its absence, an increase in the proportion of functional CcmA polymers was observed. The localization as well as the tendencies towards positive cell curvature remained unchanged, suggesting a polymer inhibitory effect mediated by the MinD. The cell elongation observed by ΔminD, as well as the shortened cell shape at ΔccmA, allows speculation about the influence of CcmA on the positioning of the FtsZ ring.
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Created: 2025Issued: 2026-01-12Updated: 2025-07-09
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Fachbereich Chemie
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Philipps-Universität Marburg
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eng
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DoctoralThesis
Keywords
in wie fern Endopeptidasen und Bactofiline und andere Strukturproteine zur Ausbildung der helikalen Morphologie beitragen. Bestimmung der intrazellulären Lokalisierung von Zell form bestimmenden Proteinen (EndopeptidasenInvestigation of the extent to which endopeptidases and bactofilins and other structural proteins contribute to the formation of helical morphology. Determination of the intracellular localization of cell shape determining proteins (endopeptidases,UntersuchungBactofiline)
DFG-subjects
helical morphologyPeptidoglycan relaxationCsd7Csd2Csd1human pathogenPeptidoglycan modificationEndopeptidaseHelicobacter pyloriBacto
DDC-Numbers
570
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Greger, Maximilian: Molecular coordination of cell shape determinants in Helicobacter pylori: Insights into the dynamics and spatial organization of peptidoglycan-modifying complexes. : Philipps-Universität Marburg 2026-01-12. DOI: https://doi.org/10.17192/z2025.0493.
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