Conformational changes at the nucleotide binding of GroEL induced by binding of protein substrates - Luminescence studies

2'-Deoxy-3'-anthraniloyl adenosine-5-triphosphate (ANT-dATP) coordinated to Tb3+ was used as an environmentally sensitive probe of the nucleotide-binding site of GroEL. Tb3+ ANT-dATP recognizes the nucleotide-binding site of GroEL and inhibits ATPase activity. Sensitized luminescence, arising from resonance energy transfer from the anthraniloyl moiety to Tb3+, is substantially enhanced in the presence of GroEL. Binding of denatured mitochondrial malate dehydrogenase to the apical domain of GroEL causes a red shift in the fluorescence emitted by anthraniloyl and, further enhancement in the phosphorescence emitted by Tb3+ upon excitation at 320 nm. It is suggested that binding of the protein substrate initiates domain movement, which is extended to the nucleotide-binding site. The luminescence results are discussed in reference to the structure of GroEL derived from x-ray crystallographic studies.