Biology subjects

Oliveira, C. G.

Publications and source records attributed to Oliveira, C. G..

3 recordsLinked to original sources

bioRxiv2025

The role of N-terminal acetylation on biomolecular condensation

N-terminal acetylation (Nt-acetylation) is one of the most prevalent co-translational modifications in eukaryotes, affecting nearly 80% of the human proteome. Despite its ubiquity, the potential impact of this phenomenon on biomolecular condensation has been largely overlooked. Here, we uncover how this chemically subtle modification can exert broad and multifaceted control over phase behaviour, using Grh1, a Golgi-associated protein involved in stress-induced secretion in yeast, as a model system. We show that Nt-acetylation increases the saturation concentration for condensation, reduces droplet size and number, dampens pH sensitivity, weakens electrostatic contributions, and suppresses water dipolar relaxation within condensates, indicating reduced internal hydration and environmental responsiveness. These effects are accompanied by acetylation-dependent dimerisation and local structural changes, including a concentration-dependent gain in -helicity. Remarkably, co- condensation assays reveal that acetylated and non-acetylated forms of the same protein are only partially miscible, giving rise to core-shell architectures driven by differences in interfacial tension. Together, our findings highlight Nt-acetylation as a potent, generalizable regulator of condensate material properties, linking primary sequence chemistry to mesoscale organisation. Given its evolutionary conservation and prevalence across eukaryotic proteomes, Nt-acetylation may represent a widespread mechanism for modulating protein condensation in health and disease.

biophysics↗

bioRxiv2023

The potential role of liquid-liquid phase separation in the cellular fate of the compartments for unconventional protein secretion

Eukaryotic cells have developed sophisticated mechanisms for biomolecule transport, particularly under stress conditions. This study focuses on the unconventional protein secretion (UPS) pathways activated during starvation stress, facilitating the export of soluble leaderless proteins. Specifically, we examine the role of the GRASP family, which is crucial in these processes but has largely unexplored mechanisms, especially regarding the biogenesis and cargo recruitment for the vesicular-like compartment for UPS. Our results reveal that under the circumstances mimicking starvation conditions in yeast, liquid-liquid phase separation (LLPS) is instrumental in the self-association of Grh1, the yeast homologue of GRASP. This association is likely a precursor to the biogenesis of the so-called Compartment for Unconventional Protein Secretion. We demonstrate that Grh1s self-association involves complex interactions and is regulated by electrostatic, hydrophobic, and hydrogen-bonding forces. Importantly, our study shows that phase-separated states of Grh1 can recruit UPS cargo under starvation-like situations, a significant finding given the minimal interaction between these proteins under normal conditions. Additionally, we address how droplet ageing might affect the ability of cells to return to normal post-stress states. Our findings can potentially enhance our understanding of intracellular protein dynamics and their adaptive responses to stress in eukaryotic cells.

biophysics↗

bioRxiv2019

The GRASP domain in Golgi Reassembly and Stacking Proteins: differences and similarities between lower and higher Eukaryotes

The Golgi complex is part of the endomembrane system and is responsible for receiving transport cargos from the endoplasmic reticulum and for sorting and targeting them to their final destination. To perform its function in higher eukaryotic cells, the Golgi needs to be correctly assembled as a flatted membrane sandwich kept together by a protein matrix. The correct mechanism controlling the Golgi cisternae assembly is not yet known, but it is already accepted that the Golgi Reassembly and Stacking Protein (GRASP) is a main component of the Golgi protein matrix. Unlike mammalian cells, which have two GRASP genes, lower eukaryotes present only one gene and distinct Golgi cisternae assembly. In this study, we performed a set of biophysical studies to get insights on both human GRASP55 and GRASP65 and compare them with GRASPs from lower eukaryotes (S. cerevisiae and C. neoformans). Our data suggest that both human GRASPs are essentially different from each other and GRASP65 is more similar to the subgroup of GRASPs from lower eukaryotes. GRASP55 is present mainly in the Golgi medial and trans faces, which are absent in both funguses, while GRASP65 is located in the cis-Golgi. We suggest that the GRASP65 gene is more ancient and the paralogue GRASP55 might have appeared latter in evolution, together with the medial and trans Golgi faces in mammalians.

biophysics↗