Small-molecule inhibition of SARS-CoV-2 NSP14 RNA cap methyltransferase.

Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The rapid development of highly effective vaccines against SARS-CoV-2 has altered the trajectory of the pandemic, and antiviral therapeutics have further reduced the number of COVID-19 hospitalizations and deaths. Coronaviruses are enveloped, positive-sense, single-stranded RNA viruses that encode various structural and non-structural proteins, including those critical for viral RNA replication and evasion from innate immunity.

Cryo-EM Structures of CRAF/14-3-3 and CRAF/14-3-3/MEK1 Complexes.

RAF protein kinases are essential effectors in the MAPK pathway and are important cancer drug targets. Structural understanding of RAF activation is so far based on cryo-electron microscopy (cryo-EM) and X-ray structures of BRAF in different conformational states as inactive or active complexes with KRAS, 14-3-3 and MEK1. In this study, we have solved the first cryo-EM structures of CRAF/14-3-3 at 3.

Studying integral membrane protein by SANS using stealth reconstitution systems.

Structural studies of integral membrane proteins (IMPs) are challenging as many of them require a lipid environment for full activity and stability. Reconstitution of IMPs into carrier systems such as nanodiscs or Salipro that mimic the native lipidic environment allow structural studies of membrane proteins in solution. The difficulty with this approach when applied to scattering techniques is the contribution of the carrier system to the scattering intensity and the subsequent challenging data analysis.

Structural Kinetics of MsbA Investigated by Stopped-Flow Time-Resolved Small-Angle X-Ray Scattering.

Recent structures of full-length ATP-binding cassette (ABC) transporter MsbA in different states indicate large conformational changes during the reaction cycle that involve transient dimerization of its nucleotide-binding domains (NBDs). However, a detailed molecular understanding of the structural changes and associated kinetics of MsbA upon ATP binding and hydrolysis is still missing. Here, we employed time-resolved small-angle X-ray scattering, initiated by stopped-flow mixing, to investigate the kinetics and accompanying structural changes of NBD dimerization (upon ATP binding) and subsequent dissociation (upon ATP hydrolysis) in the context of isolated NBDs as well as full-length MsbA in lipid nanodiscs.

Structural basis for activation of plasma-membrane Ca-ATPase by calmodulin.

Plasma-membrane Ca-ATPases expel Ca from the cytoplasm and are key regulators of Ca homeostasis in eukaryotes. They are autoinhibited under low Ca concentrations. Calmodulin (CaM)-binding to a unique regulatory domain releases the autoinhibition and activates the pump.

Conformational States of ABC Transporter MsbA in a Lipid Environment Investigated by Small-Angle Scattering Using Stealth Carrier Nanodiscs.

Structural studies of integral membrane proteins (IMPs) are challenging, as many of them are inactive or insoluble in the absence of a lipid environment. Here, we describe an approach making use of fractionally deuterium labeled "stealth carrier" nanodiscs that are effectively invisible to low-resolution neutron diffraction and enable structural studies of IMPs in a lipidic native-like solution environment. We illustrate the potential of the method in a joint small-angle neutron scattering (SANS) and X-ray scattering (SAXS) study of the ATP-binding cassette (ABC) transporter protein MsbA solubilized in the stealth nanodiscs.

Lipid-like Peptides can Stabilize Integral Membrane Proteins for Biophysical and Structural Studies.

A crucial bottleneck in membrane protein structural biology is the difficulty in identifying a detergent that can maintain the stability and functionality of integral membrane proteins (IMPs). Detergents are poor membrane mimics, and their common use in membrane protein crystallography may be one reason for the challenges in obtaining high-resolution crystal structures of many IMP families. Lipid-like peptides (LLPs) have detergent-like properties and have been proposed as alternatives for the solubilization of G protein-coupled receptors and other membrane proteins.