Analysis of the structure and interactions of the SARS-CoV-2 ORF7b accessory protein.

SARS-CoV-2 carries a sizeable number of proteins that are accessory to replication but may be essential for virus-host interactions and modulation of the host immune response. Here, we investigated the structure and interactions of the largely unknown ORF7b, a small membranous accessory membrane protein of SARS-CoV-2. We show that structural predictions indicate a transmembrane (TM) leucine zipper for ORF7b, and experimentally confirm the predominantly α-helical secondary structure within a phospholipid membrane mimetic by solid-state NMR.

Hepatitis Delta Antigen Retains the Assembly Domain as the Only Rigid Entity.

The hepatitis delta virus (HDV) S-HDAg and L-HDAg antigens are the two isoforms of the single protein encoded by the viral genome. Together with the double-stranded RNA genome they form the HDV ribonucleoprotein (RNP) complex. In the context of a divide-and-conquer approach, we used a combination of cell-free protein synthesis and proton (H)-detected fast magic angle spinning solid-state NMR at highest magnetic field to characterize S-HDAg.

Cell-Free Synthesis of Bunyavirales Proteins in View of Their Structural Characterization by Nuclear Magnetic Resonance.

The Rift Valley fever virus is one of the bunyaviruses on the WHO's priority list of pathogens that may cause future pandemics. A better understanding of disease progression and viral pathogenesis is urgently needed to develop treatments. The non-structural proteins NSs and NSm of human pathogenic bunyaviruses represent promising therapeutic targets, as they are often key virulence factors.

Do NSm Virulence Factors in the Viral Order Originate from Gn Gene Duplication?

One-third of the nine WHO shortlisted pathogens prioritized for research and development in public health emergencies belong to the order. Several species carry an NSm protein that acts as a virulence factor. We predicted the structures of these NSm proteins and unexpectedly found that in two families, their cytosolic domain was inferred to have a similar fold to that of the cytosolic domain of the viral envelope-forming glycoprotein N (Gn) encoded on the same genome fragment.

High and fast: NMR protein-proton side-chain assignments at 160 kHz and 1.2 GHz.

The NMR spectra of side-chain protons in proteins provide important information, not only about their structure and dynamics, but also about the mechanisms that regulate interactions between macromolecules. However, in the solid-state, these resonances are particularly difficult to resolve, even in relatively small proteins. We show that magic-angle-spinning (MAS) frequencies of 160 kHz, combined with a high magnetic field of 1200 MHz proton Larmor frequency, significantly improve their spectral resolution.