A bacterial PriB with weak single-stranded DNA binding activity can stimulate the DNA unwinding activity of its cognate PriA helicase

Table 4 Comparison of PriB stimulation of PriA helicase activity in E. coli and N. gonorrhoeae.

DNA Substrate	*E. coli*¹ Fold Stimulation of PriA by PriB	*N. gonorrhoeae*² Fold Stimulation of PriA by PriB
15 bp fork	ND	1.2
25 bp fork	1.0	1.7
40 bp fork	2.6	2.4
50 bp fork	10.4	ND
60 bp fork	10.8	ND
70 bp fork	~ 9	ND

¹Cadman et al. J Biol Chem 2005, 280(48):39693-39700.
²This study.
In this study, the 15 bp fork substrate is Fork 1, the 25 bp fork substrate is Fork 2, and the 40 bp fork substrate is Fork 3. The fold stimulation of PriA helicase activity by PriB is the ratio of the level of unwinding of the DNA substrate by PriA in the presence versus the absence of PriB. In Cadman et al., stimulation of E. coli PriA helicase by its cognate PriB was assayed using 200 nM PriB monomers and 5 nM PriA (20-fold excess of PriB dimers to PriA). In this study, stimulation of N. gonorrhoeae PriA helicase by its cognate PriB was assayed using 100 nM PriB monomers and 2 nM PriA (25-fold excess of PriB dimers to PriA). ND: Not determined.

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