The transport reaction catalyzed by Mer Superfamily members is: Hg2+ or methyl-Hg2+ (out) → Hg2+ or methyl-Hg2+ (in) The MerF protein encoded on plasmid pMER327/419 is an 81 residue polypeptide with two putative TMSs.

MerF has two vicinal pairs of cysteine residues which are involved in the transport of Hg(II) across the membrane and are exposed to the cytoplasm.

The MerTP permeases catalyze uptake into bacterial cells of Hg2+ in preparation for its reduction by the MerA mercuric reductase.

[3][7][8] MerP is a periplasmic Hg2+-binding receptor of about 70-80 amino acyl residues, synthesized with a cleavable N-terminal leader.

[9][10] It is 91 amino acyl residues (aas) long with its leader sequence, is monomeric, and binds a single Hg2+ ion.

[11] The MerC protein encoded on the IncJ plasmid pMERPH of the Shewanella putrefaciens mercuric resistance operon is 137 amino acids in length and possesses four putative transmembrane α-helical spanners (TMSs).

[2][12][13][14] See Kiyono, Masako; Sone, Yuka; Nakamura, Ryosuke; Pan-Hou, Hidemitsu; Sakabe, Kou (2009-04-02).