Alustalasid

Alustalasid (baseplates) are multi-protein assemblies located at the distal end of tailed bacteriophage tails. They are essential components of the infection apparatus, mediating initial contact with the bacterial surface and acting as a molecular switch that couples receptor recognition to genome delivery.

Structurally, baseplates often comprise a central platform and peripheral receptor-binding elements such as tail fibers or spikes. In many contractile-tailed phages, binding to a bacterial receptor induces conformational changes in the baseplate that propagate to the tail sheath, triggering contraction and the puncture of the cell envelope to inject DNA. In phages with non-contractile tails, baseplates provide a scaffold for enzymatic activities that breach the cell wall and help guide DNA entry.

Function and infection: During adsorption, baseplate-associated proteins recognize specific receptors on the bacterial surface, which determines host range. Receptor engagement typically initiates structural rearrangements that enable the tail tube to open and DNA to be translocated into the host.

Diversity and research: Baseplates show variation across tailed phages (Caudovirales) in composition and arrangement. They have been studied extensively by cryo-electron microscopy and X-ray crystallography, with model systems such as bacteriophage T4 offering detailed insights into baseplate architecture and its role in infection initiation.

Relevance: Understanding baseplate structure and function informs phage therapy, nanotechnology, and the broader study of virus–host interactions.