Tryptophan Residues Are Critical for Portal Protein Assembly and Incorporation in Bacteriophage P22.

The oligomerization and incorporation of the bacteriophage P22 portal protein complex into procapsids (PCs) depends upon an interaction with scaffolding protein, but the region of the portal protein that interacts with scaffolding protein has not been defined. In herpes simplex virus 1 (HSV-1), conserved tryptophan residues located in the wing domain are required for portal-scaffolding protein interactions. In this study, tryptophan residues (W) present at positions 41, 44, 207 and 211 within the wing domain of the bacteriophage P22 portal protein were mutated to both conserved and non-conserved amino acids.

Comparison of analytical techniques to quantitate the capsid content of adeno-associated viral vectors.

Adeno-associated virus (AAV) vectors, which contain a DNA transgene packaged into a protein capsid, have shown tremendous therapeutic potential in recent years. An inherent characteristic of the manufacturing process is production of empty capsids that lack the transgene and are therefore unable to provide the intended therapeutic benefit. The effect of empty capsids on clinical outcomes is not well understood, but there are immunogenicity and efficacy concerns, and these empty capsids are considered a product-related impurity.

Asymmetrizing an icosahedral virus capsid by hierarchical assembly of subunits with designed asymmetry.

Symmetrical protein complexes are ubiquitous in biology. Many have been re-engineered for chemical and medical applications. Viral capsids and their assembly are frequent platforms for these investigations.

Disassembly Intermediates of the Brome Mosaic Virus Identified by Charge Detection Mass Spectrometry.

Capsid disassembly and genome release are critical steps in the lifecycle of a virus. However, their mechanisms are poorly understood, both in vivo and in vitro. Here, we have identified two in vitro disassembly pathways of the brome mosaic virus (BMV) by charge detection mass spectrometry and transmission electron microscopy.

Multiple Pathways in Capsid Assembly.

For a three-dimensional structure to spontaneously self-assemble from many identical components, the steps on the pathway must be kinetically accessible. Many virus capsids are icosahedral and assembled from hundreds of identical proteins, but how they navigate the assembly process is poorly understood. Capsid assembly is thought to involve stepwise addition of subunits to a growing capsid fragment.

Hepatitis B Virus Capsid Completion Occurs through Error Correction.

Understanding capsid assembly is important because of its role in virus lifecycles and in applications to drug discovery and nanomaterial development. Many virus capsids are icosahedral, and assembly is thought to occur by the sequential addition of capsid protein subunits to a nucleus, with the final step completing the icosahedron. Almost nothing is known about the final (completion) step because the techniques usually used to study capsid assembly lack the resolution.

Chemical and physical transformations of aluminosilicate clay minerals due to acid treatment and consequences for heterogeneous ice nucleation.

Mineral dust aerosol is one of the largest contributors to global ice nuclei, but physical and chemical processing of dust during atmospheric transport can alter its ice nucleation activity. In particular, several recent studies have noted that sulfuric and nitric acids inhibit heterogeneous ice nucleation in the regime below liquid water saturation in aluminosilicate clay minerals. We have exposed kaolinite, KGa-1b and KGa-2, and montmorillonite, STx-1b and SWy-2, to aqueous sulfuric and nitric acid to determine the physical and chemical changes that are responsible for the observed deactivation.