Fig 3.
Effect of ybdD mutation on Nuc secretion driven by the SPExp4 under the control of the inducible promoter PnisA. NucB secretion profiles of NZ(pIL253, pLB141) and NZybdD (pLB141) are compared. Protein samples from cell (C) and supernatant (S) fractions of exponentially growing cultures induced by 1 ng/ml nisin during 1 h were analyzed by SDS-PAGE and Western blotting using anti-Nuc antibodies (A) and quantified by fluorimetry (B). Total amounts of the precursor form and both secreted forms (cell associated and released in the supernatant [NucB and NucA]) of the protein are expressed in arbitrary units (AU) corresponding to the measured signal intensity. (C) Dosage of active nuclease released in the supernatant by NZ(pIL253, pLB141) and NZybdD(pLB141) strains using a spectrophotometric Nuc assay. Data are means ± SE (n = 6). *, P < 0.05 (Mann-Whitney U test).