Immunodetection of the IMMUTANS polypeptide after expression in E. coli (A) and after sub-fractionation of purified chromoplasts from a ripening pepper fruit (B). A, Three E. coli strains were used: control (lane 1), expressing the 130 C-terminal amino acids (lane 2), or expressing the full mature polypeptide (lane 3). E. coli cells were grown and total protein recovered as described in “Materials and Methods.” In lane 3, the smear above the mature 41-kD band is due to incomplete resolubilization of the IMMUTANS polypeptide from inclusion bodies. B, Achlorophyllous membranes (Mb), membrane-wash fraction (W), low-density lipid fraction (L), and stroma (S) were fractionated as described in “Materials and Methods.” Protein samples were separated by SDS/12.5% (v/v) PAGE and transferred to nitrocellulose membranes. Position of size markers is shown on the left. The primary antibody was raised as described in “Materials and Methods.” A horseradish peroxidase-coupled secondary antibody was used. Detection was performed colorimetrically (A) or by enhanced chemiluminescence (B). Bands discussed in the text are indicated by arrowheads.