Synthesis of capsular polysaccharide at the division septum of Streptococcus pneumoniae is dependent on a bacterial tyrosine kinase

Abstract

SummaryOne of the main virulence factors of the pathogenic bacterium Streptococcus pneumoniae is the capsule, present at the bacterial surface, surrounding the entire cell. Virtually all the 90 different capsular serotypes of S. pneumoniae, which vary in their chemical composition, express two conserved proteins, Wzd and Wze, which regulate the rate of the synthesis of capsule. In this work, we show that Wzd, a membrane protein, and Wze, a cytoplasmic tyrosine kinase, localize at the bacterial division septum, when expressed together in pneumococcal cells, without requiring the presence of additional proteins encoded in the capsule operon. The interaction between the two proteins and their consequent septal localization was dependent on a functional ATP binding domain of Wze. In the absence of either Wzd or Wze, capsule was still produced, linked to the cell surface, but it was absent from the division septum. We propose that Wzd and Wze are spatial regulators of capsular polysaccharide synthesis and, in the presence of ATP, localize at the division site, ensuring that capsule is produced in co-ordination with cell wall synthesis, resulting in full encapsulation of the pneumococcal cells.

Tyrosine phosphorylation enhances activity of pneumococcal autolysin LytA

“…Indeed, we have shown that CpsD, as well as pneumococcal PTP CpsB, can act on LytA as a substrate in vitro, although as yet we have been unable to detect this in situ, probably due to low levels of LytA tyrosine phosphorylation. Previous studies illustrated that LytA as well as CpsD and BY-kinase adaptor protein CpsC locate to the septa of S. pneumoniae (De Las Rivas et al, 2002;Henriques et al, 2011;Mellroth et al, 2012), suggesting the possibility that these proteins co-localize, and further that there is a link between capsular polysaccharide synthesis and autolysis. Sun et al (2010) performed a phosphoproteomic study of the pneumococcus in which they showed that Y264 of LytA was phosphorylated.…”

“…With CpsD the only BY-kinase identified to date in S. pneumoniae, and both proteins known to localize to the cell septum (Henriques et al, 2011;Mellroth et al, 2012), we hypothesized that CpsD plays a role in the phosphorylation of LytA, and that phosphorylation regulates its amidase activity. This study shows for the first time an effect of tyrosine phosphorylation on protein function in S. pneumoniae encoded outside of the capsule locus, and provides a hitherto unidentified link between cell autolysis and capsular polysaccharide biosynthesis.…”

Wzy-Dependent Bacterial Capsules as Potential Drug Targets

“…Additionally, we recently showed that a number of defined amino acid mutations in CpsC can affect capsule polymerisation, CpsD phosphorylation and ligation of capsule to the cell wall [84]. A recent study showed that while not affecting the attachment of capsule to the cell wall, CpsC and CpsD played critical roles in the synthesis of the capsule at the division septum [85]. This did not seem to require phosphorylation of CpsD, as the C-terminal cluster of tyrosines was not required.…”

Streptococcus agalactiae Capsule Polymer Length and Attachment Is Determined by the Proteins CpsABCD

“…A protein-protein interaction between the two homologous protein Wzd (CpsC homologue) and Wze (CpsD homologue) in S. pneumoniae has been shown previously (37). Having observed that CpsD autokinase activity required the presence of CpsC, we investigated a putative interaction between CpsC and CpsD of GBS using a bacterial two-hybrid system (28) (see "Experimental Procedures" for details).…”

“…We created the mutant strains CpsC(⌬C-term) and CpsC(⌬ext), where the predicted intracellular tail (33 aa) and extracellular domain (101 aa) of CpsC were deleted. CpsD is potentially a kinase, by virtue of comparison with the orthologous proteins CapB in S. aureus (36) and Wzd in S. pneumoniae (37). The conserved catalytic residue Lys-49 was mutated into alanine, generating strain CpsD(K49A).…”