Molecular and cell biology aspects of plague

A 70-kb virulence plasmid (sometimes called pYV) enables Yersinia spp. to s urvive and multiply in the lymphoid tissues of their host. It encodes the Y op virulon, a system consisting of secreted proteins called Yops and their dedicated type III secretion apparatus called Ysc, The Ysc apparatus forms a channel composed of 29 proteins. Of these, 10 have counterparts in almost every type III system. Secretion of some Yops requires the assistance, in the bacterial cytosol, of small individual chaperones called the Syc protei ns. These chaperones act as bodyguards or secretion pilots for their partne r Yop, Yop proteins fall into two categories. Some are intracellular effect ers, whereas the others are "translocators" needed to deliver the effecters across the eukaryotic plasma membrane, into eukaryotic cells. The transloc ators (YopB, YopD, LcrV) form a pore of 16-23 Angstrom in the eukaryotic ce ll plasma membrane. The effector Yops are YopE, YopH, YpkA/YopO, YopP/ YopJ , YopM, and YopT. YopH is a powerful phosphotyrosine phosphatase playing an antiphagocytic role by dephosphorylating several focal adhesion proteins. YopE and YopT contribute to antiphagocytic effects by inactivating GTPases controlling cytoskeleton dynamics. YopP/YopJ plays an anti-inflammatory rol e by preventing the activation of the transcription factor NF-KB. It also i nduces rapid apoptosis of macrophages, Less is known about the role of the phosphoserine kinase YopO/YpkA and YopM.