Luogo: Povo 1 - aula A221
- Waldemar Vollmer
The Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University-Newcastle United Kingdom.
Gram-negative bacteria have in their periplasm a single layer of peptidoglycan, a net-like molecule made of glycan chains that are connected by short peptides. The peptidoglycan layer, also called sacculus, protects the cell from bursting due to the turgor and maintains the shape of the cell. During growth and cell division the sacculus is enlarged by the coordinated activities of peptidoglycan synthases (penicillin-binding proteins, PBPs) and hydrolases. However, the molecular mechanisms underlying peptidoglycan growth and its regulation are poorly understood.
Cytoskeletal proteins and associated cell morphogenesis proteins control peptidoglycan synthesis from inside the cell, within large cell envelope assemblies called elongasome and divisome. In Escherichia coli peptidoglycan growth is also regulated from the outside of the sacculus by outer membrane-anchored lipoproteins. LpoA and LpoB span the periplasm and are required to activate the inner membrane anchored peptidoglycan synthases, PBP1A and PBP1B, respectively. PBP1B-LpoB are involved with the synthesis of septal peptidoglycan during cell division. The Tol complex facilitates the constriction of the outer membrane during cell division utilizing the proton motive force. Recent work showed that two members of the Tol complex, CpoB and TolA, modulate the activity of PBP1B-LpoB to coordinate peptidoglycan synthesis with outer membrane constriction during cell division, illustrating the intricate mechanisms by which the cell regulates peptidoglycan synthesis.