Biology subjects

Farkas, F.

Publications and source records attributed to Farkas, F..

3 recordsLinked to original sources

bioRxiv2025

Modulation of the internal dynamics of the Homer1 EVH1 domain by putative autism-associated mutations

The EVH1 domain of the Homer1 scaffold protein interacts with the proline-rich region of Shank3, forming a key network within the postsynaptic density. Two mutations in EVH1, M65I and S97L, were suggested to be associated with autism spectrum disorder. Combining experimental and computational investigations, we show here that neither the overall structure nor the partner binding properties of the mutants exhibit substantial changes relative to the wild type. Compared to the S97L variant, the M65I mutant exhibits larger chemical shift perturbations both upon the mutation itself and during partner binding, and also shows signs of thermal destabilization. Integration of computational and NMR investigations suggests that both mutations perturb the s-ms time scale internal motions of the EVH1 domain.

molecular biology↗

bioRxiv2025

Structural modelling and dynamics of the full-length Homer1 multimer

Abstract/SummaryHomer proteins are modular scaffold molecules that constitute an integral part of the protein network within the postsynaptic density. Full-length Homer1 forms a large homotetramer via a long coiled coil region, and can interact with proline-rich target sequences with its globular EVH1 domain. Here we report an atomistic model of the full-length Homer1 tetramer along with the NMR solution structure of its EVH1 domain. Compared to the already available EVH1 structures, our NMR ensemble exhibits subtle differences, mostly in and around its partner binding region, suggesting the presence of ligand-induced conformational transitions. Molecular dynamics simulations of the long coiled coil reveal distinct regions with different stability and flexibility, with the N-terminal part of the coiled coil exhibiting the largest motions. Interestingly, this segment is highly conserved, pointing to the functional relevance of the observed dynamical features. Our results indicate previously unexplored aspects of the flexibility of the full-length Homer1 tetramer that might contribute to the dynamic rearrangements of the postsynaptic protein network linked to its functional transitions.

molecular biology↗

bioRxiv2024

Residual flexibility in the topologically constrained multivalent complex between the GKAP scaffold and LC8 hub proteins

Guanylate kinase-associated protein (GKAP) is a large postsynaptic scaffold protein bearing two closely spaced noncanonical binding sites for the bivalent dynein light chain LC8 hub protein. This might allow the formation of heterogeneous complexes with different sizes and topologies. Here, we show that a well-defined hexameric complex is formed, composed of 2 GKAP molecules and 2 LC8 dimers. Using NMR spectroscopy, we demonstrate that the LC8-binding segment of GKAP is intrinsically disordered and the flexibility of the linker region is largely retained even in the complex form. Molecular dynamics calculations suggest that besides the tightly bound residues, the hexamer also exhibits several dynamically interchanging interactions. The flanking regions of the two binding sites on GKAP exhibit different interaction patterns, hinting at additional contacts that might explain the fixed stoichiometry of the assembly. Our results demonstrate that constrained stoichiometry can coexist with substantial flexibility in a multivalent system.

molecular biology↗