An electrospray ionisation mass spectrometry (ESI-MS) study to probe the metal ion binding site in the DNA binding domain of the yeast transcriptional activator GAL4

Abstract

Electrospray ionisation mass spectrometry (ESI-MS) is used to detect metal ions and their stoichiometry of binding in the DNA binding domain of GAL4. In this analysis, the mass spectra of the apo- and metallo-proteins differ by both mass and charge, precluding the possibility of random adduct formation. Deuterium exchange NMR experiments of Zn(II)-GAL4(7-49) indicate that the binuclear metal ion structure, which is shown to have a net negative charge of -2, is the recipient of several hydrogen bonds, notably from the main-chain amide protons of the ligating cysteine residues, indicating the charge is stabilised in this manner.