Structural features of the interaction of MapZ with FtsZ and membranes in Streptococcus pneumoniae

Area of Science:

• Microbiology
• Cell Biology
• Structural Biology

Background:

• MapZ is crucial for bacterial cell division in Streptococcus pneumoniae, localizing to midcell.
• Its function is linked to positioning the cell division machinery.
• The structure and function of MapZ's extracellular domain are known, but its cytoplasmic domain remains largely uncharacterized.

Purpose of the Study:

• To investigate the structure and function of the cytoplasmic domain of MapZ.
• To elucidate the molecular mechanisms underlying MapZ's role in recruiting FtsZ to the cell mid-section.
• To understand how MapZ interacts with the bacterial cell membrane and FtsZ.

Main Methods:

• In vitro characterization of intrinsically disordered regions within the MapZ cytoplasmic domain.
• Liposome binding assays to mimic the Streptococcus pneumoniae cell membrane.
• Analysis of MapZ-FtsZ interactions, including the effect of MapZ phosphorylation.
• Structural predictions of MapZ cytoplasmic regions.

Main Results:

• Large portions of the MapZ cytoplasmic domain are intrinsically disordered, with specific regions showing a propensity to form amphipathic helices.
• These helical regions interact with model bacterial membranes (liposomes).
• The N-terminal region of MapZ directly binds FtsZ, independent of FtsZ polymerization.
• Phosphorylation of MapZ at Thr67 and Thr68 does not affect its interactions with FtsZ or liposomes.

Conclusions:

• A model is proposed where MapZ recruits FtsZ to mid-cell, with binding modulated by competition between MapZ-membrane and MapZ-FtsZ interactions.
• This tripartite complex (MapZ, FtsZ, membrane) is key to initiating divisome assembly.
• The findings shed light on the fundamental mechanisms of bacterial cytokinesis and divisome formation.