An EXAFS study of the copper accumulated by yeast cells

X-ray absorption spectroscopy has been applied to the in vivo examination of copper-resistant yeast cells. The in vivo structure of the metal-binding site of the accumulated copper has been compared to that of the purified yeast thionein. Analysis of the EXAFS spectra performed on intact yeast cells indicates that the accumulated copper is univalent and is exclusively coordinated to sulfur atoms at a distance of 219 pin with an average coordination number of 2. In contrast, the purified protein indicates a univalent copper trigonally coordinated to sulfur at a distance of 221 pm. These discrepancies are discussed in terms of copper location in the resistant yeast cells.