Pneumonia is the leading cause of infectious death in children worldwide; the World Health Organisation estimates that it killed 922 000 children under 5 in 2015 alone. The primary cause of pneumonia is Streptococcus pneumoniae infection. All serotypes of S. pneumoniae contain a highly conserved membrane-tethered lipoprotein, PsaA, which is the manganese binding protein component of a tripartite manganese ABC import system, PsaBCA. PsaA is an essential virulence factor in S. pneumoniae; its expression is crucial for both cellular adhesion and manganese uptake. A 28-amino acid long region of PsaA, called P4, is believed to mediate adhesion between the bacterium and nasopharyngeal epithelial cells. The interactions between membrane-tethered PsaA and the bacterial cell surface, and the molecular details underpinning P4-mediated adhesion are unknown. We used molecular dynamics simulations to study the interactions between the full-length PsaA lipoprotein and a model bacterial cell membrane. The simulations show that membrane-tethered PsaA consistently adopted the same orientation with respect to the bacterial membrane, which could provide insight into its adhesive and substrate-binding properties.