Table 2. Effect of overexpression of S7 and its mutant derivatives on bacterial growth.

Plasmid	Doubling time (min)
pET-21a (+)	62 ± 9
pET-21a (+)-S7	174 ± 18
pET-21a (+)-S7Δ1–17	92 ± 13
pET-21a (+)-S7Δ72–89	87 ± 9
pET-21a (+)-S7Δ138–178	144 ± 11
pET-21a (+)-S7Δ148–178	No growth
pET-21a (+)-S7R3Q	145 ± 8
pET-21a (+)-S7Q8A	95 ± 9
pET-21a (+)-S7F17G	97 ± 13
pET-21a (+)-S7K34Q	172 ± 10
pET-21a (+)-S7K35Q	96 ± 9
pET-21a (+)-S7G54S	122 ± 15
PET-21a (+)-S7Y84A	123 ± 7
pET-21a (+)-S7K113Q	117 ± 8
pET-21a (+)-S7M115G	97 ± 8
pET-21a (+)-S7K136Q	161 ± 13
pET-21a (+)-S7R142Q	167 ± 16
pET-21a (+)-S7M143A	131 ±12

BL21(DE3)/pLysS cells were transformed with plasmid pET-21a(+)-S7, containing the gene coding for wild-type S7 under control of a T7 promoter, or with derivatives of this plasmid coding for S7 mutants, and the growth rate of the bacterial cultures was monitored in the LB medium at 37°C. Doubling time values are means ± standard deviation of at least three independent experiments. Identical results were obtained with BLR(DE3)/pLysS cells (data not shown).