Expression of nisin leader hybrids in L. lactis. SDS-PAGE electrophoresis (top) and Western hybridization (bottom) using the nisin A leader antibody. (a) Extracts from cells (lanes 1, 2, 4 and 5) and TCA-precipitated culture supernatant (lane 3) from FI5876ΔnisA containing pnisAL-nsoA1IE (lane 1), pnisAL-nsoA1YK (lanes 2 and 3), pnisAL-nsoA4 (lane 4) or pUK200 (lane 5). (b) Extracts from cells (lanes 1–4 and 8) and TCA-precipitated culture supernatant (lanes 5–7) from FI5876 biosynthetic gene knockout strains containing either pnisAL-nsoA1YK (lanes 1–7) or pUK200 (lane 8). Lanes 1 and 8, FI5876ΔnisA; lanes 2 and 5, FI5876ΔnisB; lanes 3 and 6, FI5876ΔnisC; lanes 4 and 7, FI5876ΔnisCP. M, marker.