To successfully infect a bacterium, a bacteriophage (phage) must first recognise specific cell surface factors to facilitate the injection of its genome into the host. For some bacteria, production of a capsular polysaccharide layer provides protection against phage attack. However, for phages such as the Klebsiella pneumoniae targeting siphophages NPat and BMac, the capsule acts as an initial receptor mediated by lateral tail fibres that function to degrade the protective capsule (1). Following this recognition step, a secondary interaction at the cell surface with the outer membrane porin OmpK36 is essential for productive infection. The putative central tail spike proteins, gp20 and gp21 in NPat and BMac respectively, were identified through gene synteny and sequence analysis, but the interaction with the OmpK36 host receptor has yet to be validated. This study set out to validate and characterise this interaction. Initial in silico modelling revealed domain architecture to suggest gp20/gp21 acts as the baseplate hub, central tail spike, and receptor binding protein. This differs from the more well studied T5 siphophage tail in which three proteins constitute the baseplate, tail spike and receptor binding protein. Preliminary in vitro work focused on the purification of gp20 and gp21 alongside OmpK36, providing a foundation for further analysis of this interaction using both structural and biochemical techniques. It is hoped that the characterisation of this interaction and any conformational changes elicited will allow for better understanding of how phages trigger the release of their genome into a host following recognition.