Tafamidis polyneuropathy amelioration requires modest increases in transthyretin stability even though increases in plasma native TTR and decreases in non-native TTR do not predict response.

Background: TTR aggregation causes hereditary transthyretin (TTR) polyneuropathy (ATTRv-PN) in individuals with destabilised TTR variants. ATTRv-PN can be treated with ligands that bind TTR and prevent aggregation. One such ligand, tafamidis, is widely approved to treat ATTRv-PN.

Predictive model of response to tafamidis in hereditary ATTR polyneuropathy.

BACKGROUNDThe hereditary transthyretin (TTR) amyloidoses are a group of diseases for which several disease-modifying treatments are now available. Long-term effectiveness of these therapies is not yet fully known. Moreover, the existence of alternative therapies has resulted in an urgent need to identify patient characteristics that predict response to each therapy.

Kinetic versus thermodynamic control of mutational effects on protein homeostasis: A perspective from computational modeling and experiment.

The effect of mutations in individual proteins on protein homeostasis, or "proteostasis," can in principle depend on the mutations' effects on the thermodynamics or kinetics of folding, or both. Here, we explore this issue using a computational model of in vivo protein folding that we call FoldEcoSlim. Our model predicts that kinetic versus thermodynamic control of mutational effects on proteostasis hinges on the relationship between how fast a protein's folding reaction reaches equilibrium and a critical time scale that characterizes the lifetime of a protein in its environment: for rapidly dividing bacteria, this time scale is that of cell division; for proteins that are produced in heterologous expression systems, this time scale is the amount of time before the protein is harvested; for proteins that are synthesized in and then exported from the eukaryotic endoplasmic reticulum, this time scale is that of protein secretion, and so forth.

Enhanced Aromatic Sequons Increase Oligosaccharyltransferase Glycosylation Efficiency and Glycan Homogeneity.

N-Glycosylation plays an important role in protein folding and function. Previous studies demonstrate that a phenylalanine residue introduced at the n-2 position relative to an Asn-Xxx-Thr/Ser N-glycosylation sequon increases the glycan occupancy of the sequon in insect cells. Here, we show that any aromatic residue at n-2 increases glycan occupancy in human cells and that this effect is dependent upon oligosaccharyltransferase substrate preferences rather than differences in other cellular processing events such as degradation or trafficking.

Individual and collective contributions of chaperoning and degradation to protein homeostasis in E. coli.

The folding fate of a protein in vivo is determined by the interplay between a protein's folding energy landscape and the actions of the proteostasis network, including molecular chaperones and degradation enzymes. The mechanisms of individual components of the E. coli proteostasis network have been studied extensively, but much less is known about how they function as a system.

Structural and energetic basis of carbohydrate-aromatic packing interactions in proteins.

Carbohydrate-aromatic interactions mediate many biological processes. However, the structure-energy relationships underpinning direct carbohydrate-aromatic packing interactions in aqueous solution have been difficult to assess experimentally and remain elusive. Here, we determine the structures and folding energetics of chemically synthesized glycoproteins to quantify the contributions of the hydrophobic effect and CH-π interactions to carbohydrate-aromatic packing interactions in proteins.

FoldEco: a model for proteostasis in E. coli.

To gain insight into the interplay of processes and species that maintain a correctly folded, functional proteome, we have developed a computational model called FoldEco. FoldEco models the cellular proteostasis network of the E. coli cytoplasm, including protein synthesis, degradation, aggregation, chaperone systems, and the folding characteristics of protein clients.

Glycosylation of the enhanced aromatic sequon is similarly stabilizing in three distinct reverse turn contexts.

Cotranslational N-glycosylation can accelerate protein folding, slow protein unfolding, and increase protein stability, but the molecular basis for these energetic effects is incompletely understood. N-glycosylation of proteins at naïve sites could be a useful strategy for stabilizing proteins in therapeutic and research applications, but without engineering guidelines, often results in unpredictable changes to protein energetics. We recently introduced the enhanced aromatic sequon as a family of portable structural motifs that are stabilized upon glycosylation in specific reverse turn contexts: a five-residue type I β-turn harboring a G1 β-bulge (using a Phe-Yyy-Asn-Xxx-Thr sequon) and a type II β-turn within a six-residue loop (using a Phe-Yyy-Zzz-Asn-Xxx-Thr sequon) [Culyba EK, et al.

Mechanisms of protein fibril formation: nucleated polymerization with competing off-pathway aggregation.

The formation of protein fibrils, and in particular amyloid fibrils, underlies many human diseases. Understanding fibril formation mechanisms is important for understanding disease pathology, but fibril formation kinetics can be complicated, making the relationship between experimental observables and specific mechanisms unclear. Here we examine one often-proposed fibril formation mechanism, nucleated polymerization with off-pathway aggregation.

The kinetics of nucleated polymerizations at high concentrations: amyloid fibril formation near and above the "supercritical concentration".

The formation of amyloid and other types of protein fibrils is thought to proceed by a nucleated polymerization mechanism. One of the most important features commonly associated with nucleated polymerizations is a strong dependence of the rate on the concentration. However, the dependence of fibril formation rates on concentration can weaken and nearly disappear as the concentration increases.

A perspective on mechanisms of protein tetramer formation.

Homotetrameric proteins can assemble by several different pathways, but have only been observed to use one, in which two monomers associate to form a homodimer, and then two homodimers associate to form a homotetramer. To determine why this pathway should be so uniformly dominant, we have modeled the kinetics of tetramerization for the possible pathways as a function of the rate constants for each step. We have found that competition with the other pathways, in which homotetramers can be formed either by the association of two different types of homodimers or by the successive addition of monomers to homodimers and homotrimers, can cause substantial amounts of protein to be trapped as intermediates of the assembly pathway.