NSC319726 (ZMC1) is a small molecule that reactivates mutant p53 by restoration of WT structure/function to the most common p53 missense mutant (p53-R175H). We investigated the mechanism by which ZMC1 reactivates p53-R175H and provide evidence that ZMC1: 1) restores WT structure by functioning as a zinc-metallochaperone, providing an optimal concentration of zinc to facilitate proper folding; and 2) increases cellular reactive oxygen species that transactivate the newly conformed p53-R175H (via post-translational modifications), inducing an apoptotic program. We not only demonstrate that this zinc metallochaperone function is possessed by other zinc-binding small molecules, but that it can reactivate other p53 mutants with impaired zinc binding. This represents a novel mechanism for an anti-cancer drug and a new pathway to drug mutant p53.Significance: We have elucidated a novel mechanism to restore wild-type structure/function to mutant p53 using small molecules functioning as zinc-metallochaperones. The pharmacologic delivery of a metal ion to restore proper folding of a mutant protein is unique to medicinal chemistry and represents a new pathway to drug mutant p53.

Fusion of one protein domain with another is a common event in both evolution and protein engineering experiments. When insertion is at an internal site (e.g., a surface loop or turn), as opposed to one of the termini, conformational strain can be introduced into both domains. Strain is manifested by an antagonistic folding-unfolding equilibrium between the two domains, which we previously showed can be parameterized by a coupling free-energy term (ΔG X ). The extent of strain is predicted to depend primarily on the ratio of the N-to-C distance of the guest protein to the distance between ends of the surface loop in the host protein. Here, we test that hypothesis by inserting ubiquitin (Ub) into the bacterial ribonuclease barnase (Bn), using peptide linkers from zero to 10 amino acids each. ΔG X values are determined by measuring the extent to which Co 2+ binding to an engineered site on the Ub domain destabilizes the Bn domain. All-atom, unforced Langevin dynamics simulations are employed to gain structural insight into the mechanism of mechanically induced unfolding. Experimental and computational results find that the two domains are structurally and energetically uncoupled when linkers are long and that ΔG X increases with decreasing linker length. When the linkers are fewer than two amino acids, strain is so great that one domain unfolds the other. However, the protein is able to refold as dimers and higher-order oligomers. The likely mechanism is a threedimensional domain swap of the Bn domain, which relieves conformational strain. The simulations suggest that an effective route to mechanical unfolding begins with disruption of the hydrophobic core of Bn near the Ub insertion site.

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Background Barium sulfate is utilized for imaging of the gastrointestinal tract and is usually not deposited within the wall of the intestine. It is thought that mucosal injury may allow barium sulfate to traverse the mucosa, and allow deposition to occur uncommonly. Most pathology textbooks describe the typical barium sulfate deposition pattern as small granular accumulation in macrophages, and do not describe the presence of larger rhomboid crystals. This review will summarize the clinical background, radiographic, gross, and microscopic features of barium sulfate deposition in the gastrointestinal tract. A review of the PubMed database was performed to identify all published cases of barium sulfate deposition in the gastrointestinal tract that have been confirmed by pathologic examination. Conclusions A review of the literature shows that the most common barium sulfate deposition pattern in the gastrointestinal tract is finely granular deposition (30 previously described cases), and less commonly large rhomboid crystals are seen (19 cases) with or without finely granular deposition. The fine granules are typically located in macrophages, while rhomboid crystals are usually extracellular. There are various methods to support that the foreign material is indeed barium sulfate, however, only a minority of studies perform ancillary testing. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS) can be useful for definitive confirmation. This review emphasizes the importance of recognizing both patterns of barium sulfate deposition, and the histologic differential diagnosis.

68Ga–prostate-specific membrane antigen 11 (PSMA) PET/CT imaging accurately depicts metastatic prostate adenocarcinoma (PCa). Pulmonary metastases of PCa are often overlooked on follow-up imaging in patients after initial treatment and following androgen deprivation therapy. Here we present a rare case of biopsy-proven PCa pulmonary metastasis with a ground-glass appearance. The increased PSMA expression and the evolving CT features of the solid component of the ground-glass nodule detected by PSMA PET/CT imaging led to surgical resection and PET/CT-guided therapy.