Biology subjects

Paquelin, A.

Publications and source records attributed to Paquelin, A..

2 recordsLinked to original sources

bioRxiv2021

A large disordered region confers a wide spanning volume to vertebrate Suppressor of Fused as shown in a trans-species solution study.

Hedgehog (Hh) pathway inhibition by the conserved protein Suppressor of Fused (SuFu) is crucial to vertebrate development. By constrast, SuFu removal has little effect in drosophila. Previous publications showed that the crystal structures of human and drosophila SuFu consist of two ordered domains that are capable of breathing motions upon ligand binding. However, the crystal structure of human SuFu does not give information about 20 N-terminal residues (IDR1) and an eighty-residue-long disordered region (IDR2) in the C-terminus, whose function is important for the pathway repression. These two IDRs are species-dependent. We studied SuFus structure in solution, both with circular dichroism and small angle X-ray scattering, comparing drosophila, zebrafish and human species, to better understand this considerable difference. Our studies show that, in spite of similar crystal structures restricted to ordered domains, drosophila and vertebrate SuFu have very different structures in solution. The IDR2 of vertebrates spans a large area, thus enabling it to reach for partners and be accessible for post-translational modifications. Furthermore, we show that the IDR2 region is highly conserved within phyla but varies in length and sequence, with insects having a shorter disordered region while that of vertebrates is broad and mobile. This major variation may explain the different phenotypes observed upon SuFu removal.

biophysics↗

bioRxiv2021

Interaction of the TonB dependent transporter HasR with its cognate TonB-like protein HasB in a membrane environment

The envelope of Gram-negative bacteria is composed of a double membrane separated by the periplasmic space. This organization imposes geometrical and distance constraints that are key for the mechanism of action of multicomponent systems spanning the envelope. However, consideration of all three compartments by experimental approaches is still elusive. Here we used the state-of-the-art molecular dynamics simulation in an Escherichia coli envelope model to obtain a dynamic view of molecular interactions between the outer membrane heme transporter HasR and the inner membrane TonB-like protein HasB. Their interaction allows the transfer of the inner membrane proton motive force derived energy to the transporter for heme internalization. The simulations which incorporate both membranes show the key role of periplasmic domains of both proteins, and their dynamics in the complex formation and stability. They revealed a previously unidentified atomic network of interactions, as well as the sequences of the interactions and their variations with the presence of external substrates. Experimental validation (mutations, phenotypic and in vitro assays) confirms the robustness of our approach and provides verification of the simulation-predicted interactions. Based on structural and sequence conservation, the network of interaction revealed in this study is expected to occur in other nutrient import systems. The integrative approach presented here is highly useful to study the dynamic interplay between components of any other bacterial transmembrane systems.

biophysics↗