TABLE 1.

Membrane independence of R. rickettsii-induced NF-κB activation in endothelial cell extracts^a

Cellular fraction	Basal level of NF-κB in unstimulated cellsb	% Activation over basal level after incubation with R. rickettsii
600 × g supernatant (cytoplasmic extract with membranes)	1	178
105,000 × g supernatant, centrifuged for:
1 h (membrane-free cytoplasmic extract)	1.9	129
6 h (proteasome-free cytoplasmic extract)	3.3	127

^aCellular preparations were incubated with R. rickettsii for 30 min at 37°C and subsequently analyzed for DNA binding activity by EMSA. 

^bValues for NF-κB pools in different subcellular fractions, with 600 × g supernatant contents assigned a value of 1.