The use of endocytic uptake pathways to deliver poorly permeable molecules into mammalian cells is often plagued by entrapment and degradation of material in late endosomes and lysosomes. As a strategy to prevent the exposure of cargo to these highly hydrolytic membrane-sealed compartments, we synthesized derivatives of the membrane anchor N-alkyl-3beta-cholesterylamine that selectively target ...

Extracellular microbe-mineral electron transfer is a major driving force for the oxidation of organic carbon in many subsurface environments. Extracellular multi-heme cytochromes of the Shewenella genus play a major role in this process but the mechanism of electron exchange at the interface between cytochrome and acceptor is widely debated. The 1.8 Å x-ray crystal structure of the decaheme Mtr...

Disulfide bonds provide a bioactivatable connection with applications in imaging and therapy. The circulation stability and intracellular release of disulfides are problematically coupled in that increasing stability causes a corresponding decrease in cleavage and payload release. However, an antibody offers the potential for a reversible stabilization. We examined this by attaching a small mol...

The effect of mechanical force on the free-energy surface that governs a chemical reaction is largely unknown. The combination of protein engineering with single-molecule force-clamp spectroscopy allows us to study the influence of mechanical force on the rate at which a protein disulfide bond is reduced by nucleophiles in a bimolecular substitution reaction (S(N)2). We found that cleavage of a...

The unusual ascidian ability to accumulate high levels of vanadium ions at concentrations of up to 350 mM, a 10(7)-fold increase over that found in seawater, has been attracting interdisciplinary attention for a century. Accumulated V(V) is finally reduced to V(III) via V(IV) in ascidian vanadocytes. Reducing agents must therefore participate in the reduction. Previously, we identified a vanadi...

Of the numerous methods which have been used in the estimation of disulfide bonds and sulfhydryl groups in proteins and amino acids (l), the amperometric, argentimetric titration procedure, with appropriate modifications, is especially well suited for this purpose. This paper describes a modification and extension of known methods whereby these groups may be titrated in 8 M urea. The total numb...

Proteins destined to circulate in the blood are first folded and assembled in the endoplasmic reticulum of secretory cells. For antibodies, like many other serum proteins, the folding and assembly steps involve the formation of disulfide bonds. Such bonds have been thought to be static features of proteins, stabilizing domains, and linking polypeptide chains, although some cases of extracellula...

We previously reported that if murine leukemia virus particles are produced in the presence of the mild oxidizing agent disulfide-substituted benzamide-2, they fail to undergo the normal process of virus maturation. We now show that treatment of these immature particles with a reducing agent (dithiothreitol) induces their maturation in vitro, as evidenced by proteolytic cleavage of Gag, Gag-Pol...

The glutathione-insulin transhydrogenase from beef liver haa been found to promote the reductive cleavage of the disulfide bonds of insulin by simple sulfhydryl compounds such as glutathione (2). The properties of this enzyme are of interest not only because of its probable involvement in the biological regulation of the level of insulin but also because, at present, it is the only isolated mam...

Botulinum neurotoxins and tetanus are the strongest known toxins that cause neuroparalytic syndromes in botulism tetanus. This review aimed to systematize scientific data on structures mechanism of actions botulinum neurotoxins. proteins containing functional domains responsible for receptor binding, transmembrane translocation, proteolytic cleavage required exocytosis synaptic vesicles release...