MTSEA hydrobromide is a sulfhydryl-reactive compound that modifies free cysteine residues to produce a positively charged side chain similar in size to lysine.

Activation by Cd is occluded by modification with 2-aminoethyl MTS (MTSEA), indicating that Cd binds directly and specifically to the substituted cysteines.?Cd potency for the A657C mutation (EC50 = 10 M) suggests that binding involves at least two coordinating residues, whereas weaker Cd potency for L659C (EC50 = 2 mM) implies that activation does not require tight coordination by multiple side chains for this substitution.Cys modification by MTSEA reduces susceptibility to Cd activation of receptors with A8C or L10C substitutions[1].