Investigating Protein-Protein and Protein-Lipid Interaction
Protein-protein and protein-membrane interaction play a major role in various cellular functions. I have probed three such interactions. First, based on protein-protein interactions between SARS-COV-2 and human ACE2, we have designed a detection method that does not require RNA extraction or amplification. We achieve this by measuring FRET (Förster resonance energy transfer), occurring between two appropriately labeled peptides (1,2) bound to the same spike protein. Our initial results show that we do have a weak FRET signal when two peptides bind to the Receptor Binding Domain.
Another example of protein-protein interaction is amyloid aggregation. It has been a challenge to determine the structure of transient aggregation intermediates. We plan to use optical pH recycling using a photoacid to hold the system indefinitely in the transient state. I will describe our preliminary characterization of the reversibility of a photoacid molecule synthesized by us and its effect on the aggregation kinetics of the amyloid-beta peptide.
Protein lipid interaction plays a major role in the toxicity of amyloid. However, the location and arrangement of amyloid oligomers in the membrane is unknown. We probe this by following the distance-dependent modulation of triplet state relaxation dynamics of fluorescent probes (placed on the peptide) by lipids labeled with radical at different sites. Our results show that amyloid-beta inserts in lipid vesicles at a specific location that is consistent with it forming a specific structure in the membrane. I will show the results of our computational investigation of the stability of antiparallel beta-hairpin conformation, which we have earlier shown to be the relevant structure for small oligomers (3,4), in the solution phase as well as in the lipid membrane.
1)Cao et. al., Science, 2020, 370, 426-431
2)Pomplun et. al., ACS Cent. Sci., 2021, 7, 156−163
3)Chandra et. al., Biophysics J, 2017, 113, 805-816
4)Chandra et. al., Chem. Commun., 2018, 113, 7750-7753