FIG. 1.

(A) Cysteine scanning mutagenesis of the M2-1 gene. The underlined cysteine residues at position 7, 15, 21, and 96 were changed to glycine, and the mutants are denoted C96G, C15G, C21G, and C96G. (B) Three C-terminal-end truncations were engineered by the introduction of tandem stop codons, indicated by asterisks. Mutants with a truncation of 67, 46, or 17 amino acids are designated Tr67, Tr46, or Tr17.