Neurotransmitter uptake of synaptic vesicles studied by X-ray diffraction

• Published in: European biophysics journal Vol. 51; no. 6; pp. 465 - 482
• Main Authors: Komorowski, Karlo, Preobraschenski, Julia, Ganzella, Marcelo, Alfken, Jette, Neuhaus, Charlotte, Jahn, Reinhard, Salditt, Tim
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.09.2022; Springer Nature B.V
• Subjects: Biochemistry; Biological and Medical Physics; Biomedical and Life Sciences; Biophysics; Cell Biology; Electron density profiles; Free electron lasers; Life Sciences; Membrane Biology; Membrane proteins; Nanotechnology; Neurobiology; Neurotransmitters; Organelles; Original; Original Article; Polydispersity; Protein structure; Proteins; Small angle X ray scattering; Synaptic density; Synaptic vesicles; Vesicles; X-ray diffraction; X-ray scattering; Synaptic vesicles; Synchrotron and free electron laser techniques; Small angle X-ray scattering; Neurotransmitter uptake
• ISSN: 0175-7571; 1432-1017
• DOI: 10.1007/s00249-022-01609-w

The size, polydispersity, and electron density profile of synaptic vesicles (SVs) can be studied by small-angle X-ray scattering (SAXS), i.e. by X-ray diffraction from purified SV suspensions in solution. Here we show that size and shape transformations, as they appear in the functional context of these important synaptic organelles, can also be monitored by SAXS. In particular, we have investigated the active uptake of neurotransmitters, and find a mean vesicle radius increase of about 12% after the uptake of glutamate, which indicates an unusually large extensibility of the vesicle surface, likely to be accompanied by conformational changes of membrane proteins and rearrangements of the bilayer. Changes in the electron density profile (EDP) give first indications for such a rearrangement. Details of the protein structure are screened, however, by SVs polydispersity. To overcome the limitations of large ensemble averages and heterogeneous structures, we therefore propose serial X-ray diffraction by single free electron laser pulses. Using simulated data for realistic parameters, we show that this is in principle feasible, and that even spatial distances between vesicle proteins could be assessed by this approach.