Fluoroaluminates activate transducin‐GDP by mimicking the γ‐phosphate of GTP in its binding site

Abstract
Fluoride activation of the cGMP cascade of vision requires the presence of aluminum, and is shown to be mediated by the binding of one AlF‐4 to the GDP/GTP‐binding subunit of transducin. The presence of GDP in the site is required: AlF4 is ineffective when the site is empty or when GDPßS is substituted for GDP. This sensitivity to the sulfur of GDPßS suggests that AlF4 is in contact with the GDP. Striking structural similarities between AlF4 and PO4 −1 lead us to propose that AlF4 mimics the role of the γ‐phosphate of GTP.