Charged Molecules Modulate the Volume Exclusion Effects Exerted by Crowders on FtsZ Polymerization

Area of Science:

• Biochemistry
• Cell Biology
• Microbiology

Background:

• FtsZ assembly into a Z-ring is essential for bacterial cell division.
• The cellular environment is crowded, influencing protein behavior.
• Previous studies showed inert polymers promote FtsZ assembly.

Purpose of the Study:

• To investigate the impact of protein crowders on GTP-induced FtsZ cooperative assembly.
• To understand how cellular crowding modulates FtsZ polymerization dynamics.
• To explore the role of crowder charge and type in FtsZ assembly.

Main Methods:

• Fluorescence anisotropy measurements.
• Light scattering measurements.
• Studied individual and mixed protein crowders, including ovomucoid, neutral polymers, and charged proteins.
• Investigated effects of DNA and PEGs.

Main Results:

• Protein crowders increase FtsZ polymerization tendency at micromolar magnesium concentrations.
• Negatively charged protein ovomucoid showed a larger effect.
• Neutral and positively charged proteins also reduced critical assembly concentration.
• Nonadditive effects observed with mixed crowders.

Conclusions:

• Cellular crowding, particularly with protein crowders, significantly influences FtsZ assembly.
• Crowder charge plays a role, with negatively charged molecules having a pronounced effect.
• This model highlights how intracellular heterogeneity modulates Z-ring formation for bacterial division.