Biology subjects

Malinverni, D.

Publications and source records attributed to Malinverni, D..

4 recordsLinked to original sources

bioRxiv2022

Data-driven large-scale genomic analysis reveals an intricate phylogenetic and functional landscape in J-domain proteins

The 70 kDalton Heat shock protein (Hsp70) chaperone system is emerging as a central hub of the proteostasis network that helps maintain protein homeostasis in all organisms. The recruitment of Hsp70 to perform a vast array of different cellular functions is regulated by a family of co-chaperones known as J-domain proteins (JDP) that bear a small namesake J-domain, which is required to interact and drive the ATPase cycle of Hsp70s. Both prokaryotic and eukaryotic JDPs display staggering diversity in domain architecture (besides the ubiquitous J-domain), function, and cell localization. On the contrary, a relatively small number of Hsp70 paralogs exist in cells, suggesting a high degree of specificity, but also promiscuity, in the partnering between JDPs and Hsp70s. Very little is known about the JDP family, despite their essential role in cellular proteostasis, development, and the link to a broad range of human diseases. The number of JDP gene sequences identified across all kingdoms as a consequence of advancements in sequencing technology has exponentially increased, where it is now beyond the ability of careful manual curation. In this work, we first provide a broad overview of the JDP repertoire accessible from public databases, and then we use an automated classification scheme, based on Artificial Neural Networks (ANNs), to demonstrate that the sequences of J-domains carry sufficient discriminatory information to recover with high reliability the phylogeny, localization, and domain composition of the corresponding full-length JDP. By harnessing the interpretability of the ANNs, we find that many of the discriminatory sequence positions match to residues that form the interaction interface between the J-domain and Hsp70. This reveals that key residues within the J-domains have coevolved with their obligatory Hsp70 partners to build chaperone circuits for specific functions in cells.

bioinformatics↗

bioRxiv2021

Functional control of a 0.5 MDa TET aminopeptidase by a flexible loop revealed by MAS NMR

Large oligomeric enzymes control a myriad of cellular processes, from protein synthesis and degradation to metabolism. The 0.5 MDa large TET2 aminopeptidase, a prototypical protease important for cellular homeostasis, degrades peptides within a ca. 60 [A] wide tetrahedral chamber with four lateral openings. The mechanisms of substrate trafficking and processing remain debated. Here, we integrate magic-angle spinning (MAS) NMR, mutagenesis, co-evolution analysis and molecular dynamics simulations and reveal that a loop in the catalytic chamber is a key element for enzymatic function. The loop is able to stabilize ligands in the active site and may additionally have a direct role in activating the catalytic water molecule whereby a conserved histidine plays a key role. Our data provide a strong case for the functional importance of highly dynamic - and often overlooked - parts of an enzyme, and the potential of MAS NMR to investigate their dynamics at atomic resolution.

biophysics↗

bioRxiv2020

The architecture of EMC reveals a path for membrane protein insertion

Approximately 25% of eukaryotic genes code for integral membrane proteins that are assembled at the endoplasmic reticulum. An abundant and widely conserved multi-protein complex termed EMC has been implicated in membrane protein biogenesis, but its mechanism of action is poorly understood. Here, we define the composition and architecture of human EMC using biochemical assays, crystallography of individual subunits, site-specific photocrosslinking, and cryo-EM reconstruction. Our results show that EMCs cytosolic domain contains a large, moderately hydrophobic vestibule that binds a substrates transmembrane domain (TMD). The cytosolic vestibule leads into a lumenally-sealed, lipid-exposed intramembrane groove large enough to accommodate a single substrate TMD. A gap between the cytosolic vestibule and intramembrane groove provides a path for substrate egress from EMC. These findings suggest how EMC facilitates energy-independent membrane insertion of TMDs, explain why only short lumenal domains are translocated by EMC, and constrain models of EMCs proposed chaperone function.

biochemistry↗

bioRxiv2017

New Techniques for Ancient Proteins: Direct Coupling Analysis Applied on Proteins involved in Iron Sulfur Cluster Biogenesis

Direct coupling analysis (DCA) is a powerful tool based on protein evolution and introduced to predict protein fold and protein-protein interactions which has been applied also to the prediction of entire interactomes. We have used DCA to analyse three proteins of the iron-sulfur biogenesis machine, an essential metabolic pathway conserved in all organisms. We show that, although based on a relatively small number of sequences due to its distribution in genomes, we can correctly recapitulate all the features of the fold of the CyaY/frataxin family, a protein involved in the human disease Friedreichs ataxia. This result gave us confidence in the use of this tool. Application of DCA to the iron-sulfur cluster scaffold protein IscU, which has been suggested to function both as an ordered and a disordered form, allows us to clearly distinguish evolutionary traces of the structured species, suggesting that, if present in the cell, the disordered form has not left any evolutionary imprinting. We observe instead, for the first time, direct indications of how the protein can dimerize head-to-head and bind 4Fe4S clusters. Analysis of the alternative scaffold protein IscA provides strong support to a coordination of the cluster mediated by a dimeric rather than a tetrameric form as previously suggested. Our analysis also suggests the presence in solution of a mixture of monomeric and dimeric species and guide us to the prevalent one. Finally, we used DCA to analyse protein-protein interactions between some of these proteins and discuss the potentialities and the limitations of the method.

bioinformatics↗