The interaction of tumor suppressor p53 with apo-metallothionein (apo-MT) has been carried out using a flow injection-surface plasmon resonance (FI-SPR) instrument. MT was first tethered onto the carboxymethylated dextran film. Via incorporation of glycine-HCl (pH 2) to remove the sequestrated metal ions inherent in MT molecules, a more extended and open structure of apo-MT was formed. Substantial SPR angle shift corresponding to the interaction of wild-type p53 with apo-MT was observed. The interaction was originated from the binding between the free sulfhydryl groups of apo-MT and Zn(2+) of p53 with the binding constant of 1.4 x 10(8) M(-1). The specific binding of p53 to consensus double-stranded DNA was hindered after metal chelation from p53 by apo-MT. Furthermore, inhibition of the interaction between p53 and apo-MT imposed by p53/DNA complex was observed. The fluorescence measurements also revealed the binding of p53 to apo-MT, being consistent with the SPR results. Thus, SPR could potentially serve as an attractive technique for monitoring p53 conformational change and transcriptional activity regulated by the MT/apo-MT couple.