Figure 3.

Summary of the mutations obtained. (A) Functional substitutions. Shown at the bottom are the amino acid sequence of the target region (Ser-349 to Tyr-365) of SecY. Amino acid changes, specified at Left, are shown above each residue by dark gray boxes (which fully complemented secY39) and light gray boxes (which partially complemented secY39). Black boxes indicate the original amino acid. The numbers of the clones identified are shown in the boxes. (B) Dominant-negative (nonfunctional) mutations. Mutations that were obtained after screening for dominant-negative Sec phenotypes are summarized. Black boxes, substitutions; white boxes with thick frames and Δ, single residue deletions; *, the wild-type residue. The numbers of the clones identified are shown in the boxes.