Biology subjects

Assadipapari, M.

Publications and source records attributed to Assadipapari, M..

2 recordsLinked to original sources

bioRxiv2024

Open and closed conformations of a sub-80 kDa Chagas vaccine candidate defined by a cryo-EM led integrative approach

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, remains a significant global public health concern. Despite its profound health impact in both endemic and non-endemic areas, no vaccine is available, and the existing therapies are outdated, producing severe side effects. The 80kDa prolyl oligopeptidase of Trypanosoma cruzi (TcPOP) has been recently identified as a leading candidate for Chagas vaccine development. We report the first three-dimensional structure of TcPOP in open and closed conformation, at a global resolution of 3.8 and 3.6 [A] respectively, determined using single-particle cryo-electron microscopy. Multiple conformations were observed and further characterized using plasmonic optical tweezers and hydrogen-deuterium exchange mass spectrometry. To assess the immunogenic potential of TcPOP, we immunized mice and evaluated both polyclonal and monoclonal responses against the TcPOP antigen and its homologues. The results revealed invasion blocking properties of anti-TcPOP polyclonal response via parasite lysis and its cross-reactivity versus closely-related POPs but not with human homologues. We were also able to produce and characterise three monoclonal antibodies, one of which showed neutralising properties and inhibition of parasite invasion via non-lytic mechanism. Collectively, our findings provide critical structural and functional insights necessary to understand the immunogenicity of TcPOP for future Chagas vaccine development and diagnostic applications.

biophysics↗

bioRxiv2023

Structural Flexibility and Disassembly Kinetics of Single Ferritins using Optical Nanotweezers

Ferritin, a spherical protein shell assembled from 24 subunits, functions as an efficient iron storage and release system through its channels. Understanding how various chemicals affect the structural behaviour of ferritin is crucial for unravelling the origins of iron-related diseases in living organisms including humans. In particular, the influence of chemicals on ferritins dynamics and iron release is barely explored at the single-protein level. Here, by employing optical nanotweezers using double nanohole (DNH) structures, we examined the effect of ascorbic acid (reducing reagent) and pH on ferritins conformational dynamics. The dynamics of ferritin increased as the concentration of ascorbic acid approached saturation. At pH 2.0 ferritin exhibited significant structural fluctuations and eventually underwent a stepwise disassembly into fragments. This work, for the first time, tracked the disassembly pathway and kinetics of single ferritins in solution. We identified four critical fragments during its disassembly pathway, which are 22-mer, 12-mer, tetramer, and dimer subunits. Moreover, we presented the first single-molecule evidence of the cooperative disassembly of ferritin. Interrogating ferritins structural change in response to different chemicals holds importance for understanding their roles in iron metabolism, hence facilitating further development of medical treatments for the associated diseases.

biophysics↗