A rational design for hepatitis B virus X protein refolding and bioprocess development guided by second virial coefficient studies

Structural characterization with light scattering: A tool for rationally designing protein formulations

Here we explore the possibility of using light scattering technologies as an analytical tool for understanding structural features of a protein that might be responsible for initiating aggregative interactions. Using widely independent complementary experimental and computational techniques, we found that interaction parameters like K_m in particular possess good correlation with residue specific descriptors for the model protein Bovine Serum Albumin. Such information can help rationally design protein engineering and/or formulation strategies for prolonged shelf-life of such products.

A direct role for hepatitis B virus X protein in inducing mitochondrial membrane permeabilization

Hepatitis B virus X protein (HBx) acts as a multifunctional protein that regulates intracellular signalling pathways during HBV infection. It has mainly been studied in terms of its interaction with cellular proteins. Here, we show that HBx induces membrane permeabilization independently of the mitochondrial permeability transition pore complex. We generated mitochondrial outer membrane-mimic liposomes to observe the direct effects of HBx on membranes. We found that HBx induced membrane permeabilization, and the region comprising the transmembrane domain and the mitochondrial-targeting sequence was sufficient for this process. Membrane permeabilization was inhibited by nonselective channel blockers or by N-(n-nonyl)deoxynojirimycin (NN-DNJ), a viroporin inhibitor. Moreover, NN-DNJ inhibited HBx-induced mitochondrial depolarization in Huh-7 cells. Based on the results of this study, we can postulate that the HBx protein itself is sufficient to induce mitochondrial membrane permeabilization. Our finding provides important information for a strategy of HBx targeting during HBV treatment.