RESUMEN
A highly selective detection method of native protein tyrosine phosphatase 1B (PTP1B) is described using a target specific probe equipped with 1-naphthylamine (λex =330â nm, λem =445â nm). Irradiation of a mixture of PTP1B and Probeâ 1 with ultraviolet light of 280â nm (corresponding to PTP1B excitation maximum) resulted in significant fluorescence increase at 445â nm, following FRET characteristics. This phenomenon does not occur with other closely related phosphatases or cellular abundant alkaline phosphatase (APP). Probeâ 1, the most potent and selective probe, was found to competitively inhibit PTP1B (Ki ≈42â nm), whereas APP inhibition was found to be in the low micromolar range. Furthermore, Probeâ 1 discriminates between PTP1B and several other phosphatases. Here, we report real-time label-free FRET detection of pure PTP1B as well as induced human PTP1B in Escherichia coli cell lysate. In contrast to 6,8-difluoro-4-methylumbelliferyl phosphate (DiFMUP), a representative fluorescence turn-on PTP substrate, our FRET probe successfully differentiated human cervical carcinoma cell lysate, SiHa, which has a high expression level of PTP1B, from PTP1B-knockdown SiHa cell lysate (that is, siRNA was used for PTP1B knockdown).