rpoS RNA polymerase sigma factor rpoS RPOS_YEREN Sigma factors are initiation factors that promote the attachment of RNA polymerase to specific initiation sites and are then released. This sigma factor is required for the normal expression of the enterotoxin, yst, in the stationary phase. 331 MSQNTLKVNELHEDADFDENSTETEIFDEKALVEDEPTESELAEDELLAQGVTSGADATQLYLGEIGYSPLLTAEEEVYFARRALRGDVPSRRRMIESNLRLVVKIARRYSNRGLALLDLIEEGNLGLIRAVEKFDPERGFRFSTYATWWIRQTIERAIMNQTRTIRLPIHIVKELNVYLRTARELSHKLDHEPSAEEIAEQLDKPVDDVSRMLRLNERITSVDTPLGGDSEKALLDILSDENENGPEDTTQDDDMKQSIVKWLFELNAKQREVLARRFGLLGYEAATLEDVGREIGLTRERVRQIQVEGLRRLREILQAQGLSIEALFRE