Biology subjects

Metola, A.

Publications and source records attributed to Metola, A..

5 recordsLinked to original sources

bioRxiv2026

Quasi-continuous cotranslational compaction and folding of a multidomain protein

Most proteins start to fold cotranslationally as they come off the ribosome. So far, studies of cotranslational folding have focused mainly on small, single-domain proteins. Here, we have used Force Profile Analysis to study the cotranslational folding of Firefly luciferase, a complex 550-residue protein composed of an N-terminal domain (NTD) encompassing two split Rossmann folds (RF-1, RF-2) and a {beta}-roll, and a flexibly attached C-terminal domain (CTD). The folding process is characterized by a quasi-continuous series of compaction/folding steps that generate intermediate-size pulling forces on the nascent chain, punctuated by a prominent high-force event that represents the folding of the RF-2 domain, and a few low-force instances that likely indicate the formation of distinct folding intermediates. Trigger Factor interacts extensively with the nascent chain when the central part of RF-2 and the early parts of the CTD are synthesized. Our analysis uncovers a cotranslational compaction/folding process that is rich in detail and not just a simple succession of a few distinct, cooperative folding transitions.

molecular biology↗

bioRxiv2026

SARS-CoV-2 membrane protein biogenesis

Viral protein biogenesis underpins every viral life cycle stage, and elucidating these processes could reveal fundamental principles of virus-host interaction, and vulnerabilities amenable to therapeutic targeting. Here we apply biophysical, molecular, and cell biology techniques to investigate the insertion, folding, and oligomerization of the SARS-CoV-2 M protein. We describe the sequential co-translational insertion of the hydrophobic core, and demonstrate that the cytosolic C-terminal domain undergoes slower adoption of its tertiary structure. Additionally, we characterize how the transmembrane domain bundle facilitates M-protein oligomerization. Our results reveal a hydrophobic residue cluster that is essential for protein folding and co-translational dimerization. Additionally, we identify the cellular machinery responsible for targeting and inserting the M protein into the ER membrane, and chaperones and cofactors that may contribute to proper folding.

molecular biology↗

bioRxiv2024

Calmodulin acts as a chaperone during co-translational folding of the Kv7.2 channel Calcium Responsive Domain.

In vivo, the majority of nascent protein chains must begin folding during translation in order to obtain their native structure. While the importance of co-translational folding has become increasingly clear, the specific mechanisms underlying the coordination between the ribosome, nascent chain and molecular chaperones are still uncertain. Here, we have constructed a model of the co-translational folding pathway of the calcium responsive domain (CRD) of the human neuronal KV7.2 human neuronal ion channel, showing that calmodulin (CaM) is crucial. By combining Force Profile Analysis and single-molecule force spectroscopy techniques, we found that CaM, in a calcium-dependent manner, affects early folding events involving three key -helices in the CRD. In addition, this study suggests that CaM at early stages induces the formation of metastable hairpins, as a part of the co-translational folding pathway. These findings expand on the role of CaM as a key regulator of folding in eukaryotes: not only as an essential cellular signaling protein, but also as a bona fide co-translational molecular chaperone.

molecular biology↗

bioRxiv2024

Cotranslational membrane insertion of the voltage-sensitive K+ channel KvAP

Voltage-sensor domains (VSDs), found in many voltage-sensitive ion channels and enzymes, are composed of four transmembrane helices (TMHs), including the atypical, highly positively charged S4 helix. VSDs are cotranslationally inserted into the membrane, raising the question of how the highly charged S4 helix is integrated into the lipid bilayer as it exits the ribosome. Here, we have used Force Profile Analysis to follow the cotranslational insertion of the six-TMH KvAP voltage-sensitive ion channel into the E. coli inner membrane. We find that the insertion process proceeds through three semi-independent steps: (i) insertion of the S1-S2 helix hairpin, (ii) insertion of the S3-S5 helices, and (iii) insertion of the Pore and S6 helices. Our analysis highlights the importance of the concerted insertion of helical hairpins, the dramatic influence of the positively charged residues in S4, and the unexpectedly strong forces and effects on downstream TMHs elicited by amphipathic and re-entrant helices.

molecular biology↗

bioRxiv2020

Residue-by-residue analysis of cotranslational membrane protein integration in vivo

We follow the cotranslational biosynthesis of three multi-spanning E. coli inner membrane proteins in vivo using high-resolution Force Profile Analysis. The force profiles show that the nascent chain is subjected to rapidly varying pulling forces during translation, and reveal unexpected complexities in the membrane integration process. We find that an N-terminal cytoplasmic domains can fold in the ribosome exit tunnel before membrane integration starts, that charged residues and membrane-interacting segments such as re-entrant loops and surface helices flanking a transmembrane helix (TMH) can advance or delay membrane integration, and that point mutations in an upstream TMH can affect the pulling forces generated by downstream TMHs in a highly position-dependent manner, suggestive of residue-specific interactions between TMHs during the integration process.

molecular biology↗