Bacterial cell wall: thinking globally, actin locally

Abstract

The bacterial actin-like protein MreB is thought to form a continuous helical polymer at the membrane to confer rod shape. Two new studies now show that MreB forms discrete dynamic patches that travel circumferentially.

Figure 1

Schematic representation of mobile patches of peptidoglycan elongation machinery/MreB. (A) Whole cell with glycan strands represented in red, the cytoplasmic membrane in blue, and the circumferential paths followed by peptidoglycan elongation machinery/MreB paralog complexes in black. Traveling macromolecular complexes are depicted as double-dotted structures, and green arrows depict opposite directionality of two complexes. (B) Expanded view of one processive peptidoglycan elongation machinery/MreB complex synthesizing a new glycan strand. MreB, Mbl and MreBH form polymers along the patch, and localize at the inside edge of the membrane, represented by phospholipids. The peptidoglycan elongation machinery proteins interact with the MreB homologs. An old glycan strand serves as template for synthesis of the new strand. The peptide cross-links between the glycan strands are represented by black ovals. The arrow indicates the traveling direction.