Figure 7.

Zeolin(Cys⁻) Is Secreted.

Protoplasts prepared from leaves of wild-type tobacco were transfected with either pDHA plasmid (control) or pDHA containing the coding sequence of zeolin or zeolin(Cys⁻). Transfected protoplasts were pulse-labeled with [³⁵S]Met and [³⁵S]Cys for 1 h and subjected to chase for the indicated times. Total homogenates were prepared from protoplasts or incubation medium, using homogenation buffer supplemented either with 2-ME ([B] and medium in [A]) or without the reducing agent (protoplasts in [A]), and immunoselected using anti-phaseolin antiserum. Analysis was by SDS-PAGE and fluorography. The gel in (A) was exposed for 10 d, and that in (B) was exposed for 5 d. The positions of zeolin and zeolin(Cys⁻) (arrowheads) and of the 45-kD form (arrow) are indicated. Numbers at left indicate the positions of molecular mass markers in kD.