PBP2+(mrdA)

__**PBP2 (MrdA)**__

PBP2 is a class B high molecular mass (HMM) penicillin binding protein. It is a monofunctional transpeptidase, required for the formation of the elongase potein complex which is specific to cell elongation (Vollmer and Bertsche, 2008).

__**Function:**__ PBP2 serves as a monofunctional transpeptidase enzyme, essential for the cell elongation and maintenance of the rod shape of E. coli. Inhibition of PBP2 with mencillinam leads to the formation of spherical cells, with constitutive septal murein synthesis (i.e. the murein constantly forms septums between cells) that are unable to form colonies. Hence, it is thought that PBP2 also plays an additional, essential role in regulation of septation. This role may involve the initiation of cell division and corresponding maintenance of cell diameter (Vollmer and Bertsche, 2008).

__**Structure:**__ As a HMM PBP, PBP2 posses a cytoplasmic tail, a transmembrane anchor and two domains located on the outer surface of the cytoplasmic membrane joined by a beta-rich linker. The C-terminal penicillin binding domain of PBP2 has a transpeptidase activity, allowing it to catalyse the peptide cross-linking reaction between adjacent glycan strands. Since it is a member of the class B HMM PBBs, the N-terminal domain of PBP2 does not possess glycosyltransferase activity. Instead, it is believed to play a role in cell morphogenesis by interacting with other proteins involved in the cell cycle.

__**Location:**__ PBP2, like all PBPs is located in the periplasm. It is not a stable part of the divisome complex?