Full NMR assignment, revised structure and biosynthetic analysis for the capsular polysaccharide from Streptococcus Pneumoniae serotype 15F

Upon investigation of Streptococcus pneumoniae serotype 15F capsular polysaccharide (CPS), we discovered that it had a different phosphorylation substituent, namely glycerol-2-phosphate like the other serogroup 15 CPS rather than the originally reported 0.2 equivalent of phosphate or phosphocholine. Furthermore, we also determined the locations of the two previously unassigned O-acetyl groups present in the repeating unit of the 15F CPS, and carried out full NMR assignments of the 15F as well as 15A CPS. Lastly, a biosynthetic analysis of serotypes 15F and 15A was performed and used to make a prediction for the structure of the recently discovered serotype 15D. [Display omitted] •The capsular polysaccharide structure of S. pneumoniae serotype 15F was revised.•The phosphorylation was updated and matches the remaining serogroup 15 serotypes.•Full NMR assignment of the CPS of serotype 15F and 15A was carried out.•Biosynthetic analysis of CPS genes was performed and the structure of 15D predicted.