A C-terminal disulfide bridge in pediocin-like bacteriocins renders bacteriocin activity less temperature dependent and is a major determinant of the antimicrobial spectrum.
Several lactic acid bacteria produce so-called pediocin-like bacteriocins that share sequence characteristics, but differ in activity and target cell specificity. The significance of a C-terminal disulfide bridge present in only a few of these bacteriocins was studied by site-directed mutagenesis of pediocin PA-1 (which naturally contains the bridge) and sakacin P (which lacks the bridge). Introduction of the C-terminal bridge into sakacin P broadened the target cell specificity of this bacteriocin, as illustrated by the fact that the mutants were 10 to 20 times more potent than the wild-type toward certain indicator strains, whereas the potency toward other indicator strains remained essentially unchanged. Like pediocin PA-1, disulfide-containing sakacin P mutants had the same potency at 20 and 37 degrees C, whereas wild-type sakacin P was approximately 10 times less potent at 37 degrees C than at 20 degrees C. Reciprocal effects on target cell specificity and the temperature dependence of potency were observed upon studying the effect of removing the C-terminal disulfide bridge from pediocin PA-1 by Cys-->Ser mutations. These results clearly show that a C-terminal disulfide bridge in pediocin-like bacteriocins contributes to widening of the antimicrobial spectrum as well as to higher potency at elevated temperatures. Interestingly, the differences between sakacin P and pediocin PA-1 in terms of the temperature dependency of their activities correlated well with the optimal temperatures for bacteriocin production and growth of the bacteriocin-producing strain.
Fimland
G
G
Department of Biochemistry, University of Oslo, Oslo, Norway. gunnar.fimland@biokjemi.uio.no
Johnsen
L
L
Axelsson
L
L
Brurberg
M B
MB
Nes
I F
IF
Eijsink
V G
VG
Nissen-Meyer
J
J
D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D001430:Bacteriocins / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004220:Disulfides; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D000070017:Pediocins; D013329:Structure-Activity Relationship; D013696:Temperature
D000900:Anti-Bacterial Agents; D001430:Bacteriocins; D004220:Disulfides; D000070017:Pediocins; C074288:pediocin PA-1; C087217:sakacin P protein, Lactobacillus