Structure and assembly mechanism of virus-associated pyramids

Abstract

Viruses have developed intricate molecular machines to infect, replicate within and escape from their host cells. Perhaps one of the most intriguing of these mechanisms is the pyramidal egress structure that has evolved in archaeal viruses, such as SIRV2 or STIV1. The structure and mechanism of these virus-associated pyramids (VAPs) has been studied by cryo-electron tomography and complementary biochemical techniques, revealing that VAPs are formed by multiple copies of a virus-encoded 10-kDa protein (PVAP) that integrate into the cell membrane and assemble into hollow, sevenfold symmetric pyramids. In this process, growing VAPs puncture the protective surface layer and ultimately open to release newly replicated viral particles into the surrounding medium. PVAP has the striking capability to spontaneously integrate and self-assemble into VAPs in biological membranes of the archaea, bacteria and eukaryotes. This renders the VAP a universal membrane remodelling system. In this review, we provide an overview of the VAP structure and assembly mechanism and discuss the possible use of VAPs in nanobiotechnology.

Architecture and modular assembly of Sulfolobus S-layers revealed by electron cryotomography

“…It may be speculated that distinct S-layer surface structures have evolved to modulate the cell-adhesive properties of different archaeal species. In addition, S-layers may act as receptors in cell-cell recognition or phage infection (23), and we could show previously that archaeal viruses evolved elaborate cell entry and egress strategies to overcome the S-layer barrier (24–26). It is therefore conceivable that distinct S-layer topologies provide unique recognition tags for species-specific interaction and communication and that the evolution of new structures is a manifestation of the cell’s strategy to avoid viral infection (27).…”

Architecture and modular assembly ofSulfolobusS-layers revealed by electron cryo-tomography

“…This was expected, as roughly round shapes cannot be contained in a hexagonal lattice unless 116 defects are included (D Pum, Messner, & Sleytr, 1991). Moreover, gaps in the lattice are needed 117 to accommodate surface filaments such as archaella (Daum et al, 2017) or to allow the cells to 118 grow and divide. In tomographic slices perpendicular to the membrane plane, S-layers formed 119 regular, corrugated canopy-like arrays at a centre-to-centre distance of ~30 nm from the 120 membrane ( Fig.…”

“…by S-layer pores. Thus, the S-layer will have to be partially disassembled or adopt a different local 357 geometry wherever these filaments emerge from the cell body (Daum et al, 2017). Finally, it is 358 safe to assume that due to their porosity, S-layers provide a semi-permeable barrier, similar to 359 the outer membrane of Gram-negative bacteria, albeit with a more liberal molecular weight cut-360 off.…”

Foreword to ‘Multiscale structural biology: biophysical principles and mechanisms underlying the action of bio-nanomachines’, a special issue in Honour of Fumio Arisaka’s 70th birthday

“…The Fig. 1 Example of a bionanomachine reviewed in this series (Quax and Daum 2018). Virus-associated pyramids (VAPs) are built by the selfassembly of a single type of small 10 kDa viral protein known as pVAP.…”

“…Although providing a number of advantages, the promotion did not affect Fumio as much as it might have a much younger scientist. Fumio was already the leader of his field in Japan and one of the elite researchers in phage biology worldwide (as evidenced by a number of contributions to this special issue from office holders of the International Society for Phage Biology (Quax and Daum 2018;Hyman and van Raaij 2018;Dowah and Clokie 2018;Serwer et al 2018)). Similarly, he was at the top of the tree with regard to expertise in biophysical characterization as could be easily shown by the long line of researchers within Japan wanting to collaborate with him.…”