Expression phenotypes suggest that Der participates in a specific, high affinity interaction with membranes

Area of Science:

• Bacterial cell biology
• Molecular microbiology
• Protein-membrane interactions

Background:

• GTPase Der is a unique, universally conserved bacterial protein with two tandem GTP-binding domains.
• Its precise cellular function and localization remain incompletely understood.

Purpose of the Study:

• To investigate the cellular localization and function of the bacterial GTPase Der.
• To elucidate the role of Der's unique structural domains in its cellular activities.

Main Methods:

• Fractionation of overexpressed Der from bacterial cell lysates using sucrose gradient centrifugation.
• Assessing membrane association via co-migration assays under denaturing conditions.
• Evaluating cell wall structure using microscopy in cells with altered Der expression or mutations.
• Site-directed mutagenesis of GTP-binding domains.

Main Results:

• Der specifically associates with bacterial membrane fractions with high affinity.
• Overexpression of Der leads to cell wall structural disruption at both poles, dependent on domain three.
• Mutations affecting nucleotide binding in either GTP-binding domain cause defects at a single cell pole.

Conclusions:

• Der exhibits specific, high-affinity membrane association.
• Der plays a critical role in bacterial cell wall integrity, with distinct domain functions.
• Der may mediate a functional cycle between ribosomes and the membrane in Escherichia coli.