Cryo-EM analysis of complement C3 reveals a reversible major opening of the macroglobulin ring.

The C3 protein is the central molecule within the complement system and undergoes proteolytic activation to C3b in the presence of pathogens. Pattern-independent activation of C3 also occurs via hydrolysis, resulting in C3(HO), but the structural details of C3 hydrolysis remain elusive. Here we show that the conformation of the C3(HO) analog, C3MA, is indistinguishable from C3b.

Importance of an N-terminal structural switch in the distinction between small RNA-bound and free ARGONAUTE.

ARGONAUTE (AGO) proteins bind to small non-coding RNAs to form RNA-induced silencing complexes. In the RNA-bound state, AGO is stable while RNA-free AGO turns over rapidly. Molecular features unique to RNA-free AGO that allow its specific recognition and degradation remain unknown.

The Myotubularin Related Proteins and the Untapped Interaction Potential of Their Disordered C-Terminal Regions.

Intrinsically disordered regions (IDRs) of proteins remain understudied with enigmatic sequence features relevant to their functions. Members of the myotubularin-related protein (MTMR) family contain uncharacterized IDRs. After decades of research on their phosphatase activity, recent work on the C-terminal IDRs of MTMR7 revealed new interactions and important new functions beyond the phosphatase function.

Stereochemistry in the disorder-order continuum of protein interactions.

Intrinsically disordered proteins can bind via the formation of highly disordered protein complexes without the formation of three-dimensional structure. Most naturally occurring proteins are levorotatory (L)-that is, made up only of L-amino acids-imprinting molecular structure and communication with stereochemistry. By contrast, their mirror-image dextrorotatory (D)-amino acids are rare in nature.

On the use of dioxane as reference for determination of the hydrodynamic radius by NMR spectroscopy.

Measuring the compaction of a protein or complex is key to our understanding of the interactions within and between biomolecules. Experimentally, protein compaction is often probed either by estimating the radius of gyration (R) obtained from small-angle x-ray scattering (SAXS) experiments or the hydrodynamic radius (R) obtained, for example, by pulsed field gradient NMR (PFG NMR) spectroscopy. PFG NMR experiments generally report on the translational diffusion coefficient, which in turn can be used to estimate R using an internal standard to account for sample viscosity and uncertainty about the gradient strength.