Table 1.

mRNA folding energies of the AGGAGG ribosome binding site and activities of secreted nuclease and α-amylase of selected clones from the Usp45sp silent mutation library^a

Usp45sp silent mutation clone	ΔG of ribosome binding site (AGGAGG)	Secreted nuclease activity (compared to Usp45sp)b	Secreted α-amylase activity (% of Usp45sp)c
Usp45SM2	−8.4	−	79 ± 5††
Usp45SM14	−8.4	−−	83 ± 13
Usp45SM11	−6.1	−−	85 ± 3††
Usp45sp	−6.1	*	100
Usp45SM16	−5.9	−	91 ± 12
Usp45SM19	−5.9	+	106 ± 16
Usp45SM4	−5.7	+	107 ± 6
Usp45SM10	−3.8	+	116 ± 5†
Usp45SM20	−3.7	++	103 ± 15
Usp45SM5	−3.7	+	113 ± 5†
Usp45SM8	−3.3	+	92 ± 5
Usp45SM15	−3.3	+	100 ± 6
Usp45SM9	−3.3	+	114 ± 7
Usp45SM7	−3.2	+	105 ± 14
Usp45SM6	−2.5	++	99 ± 12
Usp45SM12	−1.6	++	96 ± 12
Usp45SM3	−0.6	*	114 ± 3††

^aNuclease and α-amylase secretion levels are reported for cultures induced with 10 ng/ml nisin for 2 h at mid-log phase. ΔG, mRNA folding energy. Nucleotide sequences are given in Table S4 in the supplemental material.

^bData represent levels of nuclease secretion. *, secretion similar to Usp45sp level; −, secretion slightly (<10%) lower than Usp45sp level; −−, secretion much (>10%) lower than Usp45sp level; +, secretion slightly (<10%) higher than Usp45sp level; ++, secretion much (>10%) higher than Usp45sp level.

^cα-Amylase secretion data represent the means ± standard errors of the means (SEM) of the results of three independent experiments. †, P < 0.05; ††, P < 0.01 (for statistical comparison of α-amylase activities of the respective clone and Usp45sp using one-tailed Student's t test).