Fig. 1.

Space-fill models of Cys S-conjugates of Hg²⁺ and CH₃Hg⁺ compared with the amino acids, cystine, and methionine. The Cys S-conjugate of Hg²⁺ (Cys-S-Hg-S-Cys) is similar in shape and size to cystine, while the Cys S-conjugate of CH₃Hg⁺ (CH₃Hg⁺-SCys) is similar to methionine. Owing to these similarities, it has been hypothesized that Cys- S-Hg-S-Cys and Cys-S-CH₃Hg⁺ are transportable substrates of carrier proteins that mediate the transport of cystine and methionine, respectively