Fig 6.

SlaP occurs as soluble and membrane-associated species in B. anthracis. Vegetative forms of B. anthracis Sterne and the slaP mutant were grown to the mid-log phase. Cultures were centrifuged to sediment vegetative forms, which were subsequently lysed in a bead beater. Beads and unbroken cells were removed by slow-speed centrifugation, and crude extracts were subjected to ultracentrifugation at 100,000 × g, separating soluble cytoplasmic proteins in the supernatant (S) from membrane proteins in the pellet (P). Membranes were extracted on ice with 0.1 M Na₂CO₃ and again subjected to ultracentrifugation at 100,000 × g, separating peripheral membrane proteins in the supernatant from integral membrane proteins in the pellet. All samples were analyzed with Coomassie-stained 10% SDS-PAGE gels and by immunoblotting with SlaP-specific rabbit antiserum.