Biology subjects

Allison, T. M.

Publications and source records attributed to Allison, T. M..

4 recordsLinked to original sources

bioRxiv2024

Cardiac stress leads to regulation of Filamin C dimerisation via an ancient phosphorylation-modulated interaction with HSPB7

The biomechanical properties and responses of tissues underpin a variety of physiological functions and pathologies. In striated muscle, the actin-binding protein filamin C (FLNC) is a key protein whose variants causative for a wide range of cardiomyopathies and musculoskeletal pathologies. Seemingly a multi-functional protein that interacts with a variety of partners, how FLNC is regulated at the molecular level is not well understood. Here we have investigated its interaction with HSPB7, a cardiac-specific molecular chaperone whose absence is embryonically lethal. We found that FLNC and HSPB7 interact in cardiac tissue under biomechanical stress, forming a strong hetero-dimer whose structure we have solved by means of X-ray crystallography. Our quantitative analyses show that the hetero-dimer out-competes the FLNC homo-dimer interface, potentially acting to abrogate the ability of the protein to cross-link the actin cytoskeleton, and to enhance its diffusive mobility. We show that phosphorylation of FLNC at threonine 2677, located at the dimer interface and associated with cardiac stress, acts to favour the homo-dimer. Conversely, phosphorylation at tyrosine 2683, also at the dimer interface, has the opposite effect and shifts the equilibrium towards the hetero-dimer. Evolutionary analysis and ancestral sequence reconstruction reveals this interaction and its mechanisms of regulation to date around the time primitive hearts evolved in chordates. Our work rationalises on the molecular level how FLNC might switch between stabilising functions in the cell, and reveals how HSPB7 acts as a specific molecular chaperone that regulates FLNC.

molecular biology↗

bioRxiv2022

A grappling hook interaction balances self-assembly and chaperone activity of Nucleophosmin 1

How the self-assembly of partially disordered proteins generates functional compartments in the cytoplasm and particularly in the nucleus is poorly understood. Nucleophosmin 1 (NPM1) is an abundant nucleolar protein that forms large oligomers which provide the scaffold for ribosome assembly but also prevent protein aggregation as part of the cellular stress response. Examining the relationship between the self-assembly and chaperone activity of NPM1, we find that oligomerization of full-length NPM1 modulates its ability to retard amyloid formation in vitro. Machine learning and cryo-electron microscopy reveal fuzzy interactions between the disordered region and the C-terminal nucleotide-binding domain that cross-link NPM1 pentamers into oligomers. Ribosomal peptides mediate in a tighter association within the oligomers, reducing their capacity to prevent amyloid formation. We conclude that NPM1 uses a "grappling hook" interaction to form a network-like structure whose chaperone activity is tuned by basic proteins, suggesting a regulatory mechanism for the nucleolar stress response.

biophysics↗

bioRxiv2022

Allosteric inhibition of Staphylococcus aureus MenD by 1,4-dihydroxy naphthoic acid: A feedback inhibition mechanism of the menaquinone biosynthesis pathway

Menaquinones (MKs) are electron carriers in bacterial respiratory chains. In Staphylococcus aureus (Sau), MKs are essential for aerobic and anaerobic respiration. As MKs are redox-active, their biosynthesis likely requires tight regulation to prevent disruption of cellular redox balance. We recently found that the Mycobacterium tuberculosis MenD, the first committed enzyme of the MK biosynthesis pathway, is allosterically inhibited by the downstream metabolite 1,4-dihydroxy-2-naphthoic acid (DHNA). To understand if this is a conserved mechanism in phylogenetically distant genera that also utilize MK, we investigated whether the Sau-MenD is allosterically inhibited by DHNA. Our results show that DHNA binds to and inhibits SEPHCHC synthase activity of Sau-MenD enzymes. We identified residues in the DHNA binding pocket that are important for catalysis (Arg98, Lys283, Lys309) and inhibition (Arg98, Lys283). Furthermore, we show that exogenous DHNA inhibits growth of Sau, an effect that can be rescued by supplementing the growth media with MK-4. Our results demonstrate that despite a lack of strict conservation of the DHNA-binding pocket between Mtb-MenD and Sau-MenD, feedback inhibition by DHNA is a conserved mechanism in Sau-MenD and hence the Sau MK biosynthesis pathway. These findings may have implications for the development of anti-staphylococcal agents targeting MK biosynthesis

biochemistry↗

bioRxiv2022

Complementing machine learning-based structure predictions with native mass spectrometry

The advent of machine learning-based structure prediction algorithms such as AlphaFold2 (AF2) has moved the generation of accurate structural models for the entire cellular protein machinery into the reach of the scientific community. However, structure predictions of protein complexes are based on user-provided input and may therefore require experimental validation. Mass spectrometry (MS) is a versatile, time-effective tool that provides information on post-translational modifications, ligand interactions, conformational changes, and higher-order oligomerization. Using three protein systems, we show that native MS experiments can uncover structural features of ligand interactions, homology models, and point mutations, that are undetectable by AF2 alone. We conclude that machine learning can be complemented with MS to yield more accurate structural models on the small and the large scale.

biophysics↗