Elucidation of the ATP7B N-Domain Mg2+-ATP Coordination Site and Its Allosteric Regulation

The diagnostic of orphan genetic disease is often a puzzling task as less attention is paid to the elucidation of the pathophysiology of these rare disorders at the molecular level. We present here a multidisciplinary approach using molecular modeling tools and surface plasmonic resonance to study the function of the ATP7B protein, which is impaired in the Wilson disease. Experimentally validated in silico models allow the elucidation in the Nucleotide binding domain (N-domain) of the Mg2+-ATP coordination site and answer to the controversial role of the Mg2+ ion in the nucleotide binding process. The analysis of protein motions revealed a substantial effect on a long flexible loop branched to the N-domain protein core. We demonstrated the capacity of the loop to disrupt the interaction between Mg2+-ATP complex and the N-domain and propose a role for this loop in the allosteric regulation of the nucleotide binding process

Single-Molecule Imaging of Recycling Synaptic Vesicles in Live Neurons

The capacity of neurons to communicate and store information in the brain critically depends on neurotransmission, a process which relies on the release of chemicals called neurotransmitters stored in synaptic vesicles at the presynaptic nerve terminals. Following their fusion with the presynaptic plasma membrane, synaptic vesicles are rapidly reformed via compensatory endocytosis. The investigation of the endocytic pathway dynamics is severely restricted by the diffraction limit of light and, therefore, the recycling of synaptic vesicles, which are roughly 45 nm in diameter, has been primarily studied with electrophysiology, low-resolution fluorescence-based techniques, and electron microscopy. Here, we describe a recently developed technique we named subdiffractional tracking of internalized molecules (sdTIM) that can be used to track and study the mobility of recycling synaptic vesicles in live hippocampal presynapses. The chapter provides detailed guidelines on the application of the sdTIM protocol and highlights controls, adaptations, and limitations of the technique