Identification of pneumococcal proteins that are functionally linked to penicillin‐binding protein 2b (PBP2b)

Abstract

The oval shape of pneumococci results from a combination of septal and lateral peptidoglycan synthesis. The septal cross-wall is synthesized by the divisome, while the elongasome drives cell elongation by inserting new peptidoglycan into the lateral cell wall. Each of these molecular machines contains penicillin-binding proteins (PBPs), which catalyze the final stages of peptidoglycan synthesis, plus a number of accessory proteins. Much effort has been made to identify these accessory proteins and determine their function. In the present paper we have used a novel approach to identify members of the pneumococcal elongasome that are functionally closely linked to PBP2b. We discovered that cells depleted in PBP2b, a key component of the elongasome, display several distinct phenotypic traits. We searched for proteins that, when depleted or deleted, display the same phenotypic changes. Four proteins, RodA, MreD, DivIVA and Spr0777, were identified by this approach. Together with PBP2b these proteins are essential for the normal function of the elongasome. Furthermore, our findings suggest that DivIVA, which was previously assigned as a divisomal protein, is required to correctly localize the elongasome at the negatively curved membrane region between the septal and lateral cell wall.

Suppression and synthetic‐lethal genetic relationships of ΔgpsB mutations indicate that GpsB mediates protein phosphorylation and penicillin‐binding protein interactions in Streptococcus pneumoniaeD39

“…These results suggest that domesticated laboratory strain R800 contains mutations that suppress primary phenotypes caused by Δ gpsB deletions and by mutations in other cell division genes (see Land and Winkler, ; Land et al ., ; Tsui et al ., ). As another example of these strain differences, changes of the single threonine residue in DivIVA (T201A) phosphorylated by StkP result in no morphology phenotype in D39 and two unencapsulated laboratory strains, R6 and Rx1, that were distantly derived from D39 (data not shown; Massidda et al ., ; Straume et al ., ), but cause cell elongation and polar bulges in R800 (Fleurie et al ., ). The normal frequency of transformation and colony morphology observed during construction of divIVA (T201A) mutants in D39 strains are not indicative of suppressor accumulation (data not shown).…”

“…The shorter and rounder appearance of Spn Δ divIVA mutant cells in chains (Fig. ) suggests a defect in peripheral or in polar PG biosynthesis, as proposed in several articles (Fadda et al ., ; Fleurie et al ., ; Massidda et al ., ; Boersma et al ., ; Straume et al ., ), but the exact function of DivIVA in Spn remains to be determined.…”

“…S14). This interaction between GpsB and MreC implicates GpsB in interacting with and regulating the peripheral PG synthesis machine that includes MreC, MreD, bPBP2b, RodA, MltG, aPBP1a, RodZ and CozE (Philippe et al ., ; Fenton et al ., ; Straume et al ., ; Tsui et al ., ). In support of this conjecture, GpsB or StkP pulls down essential bPBP2b required for peripheral PG synthesis (Fig.…”

CozEa and CozEb play overlapping and essential roles in controlling cell division in Staphylococcus aureus

“…In these cells, positioning of the Z‐ring at mid‐cell has been shown to depend on several factors, including the chromosomal origin of replication (van Raaphorst et al, ) and the peptidoglycan binding protein MapZ (Fleurie et al, ; Holeckova et al, ). Most likely, the septal and peripheral cell wall growth in pneumococcal cells are mediated by separate protein machineries, whose actions are tuned by different regulatory proteins, such as StkP, MreCD, GpsB, DivIVA and EloR (Beilharz et al, ; Fleurie et al, ; Ducret and Grangeasse, ; Rued et al, ; Stamsås et al, ; Straume et al, ; Zheng et al, ). Another protein involved in regulation of cell wall synthesis in pneumococci, named CozE (for coordinator of zonal elongation, SPD_0768 in strain D39 and Spr0777 in strain R6), was recently identified (Fenton et al, ; Straume et al, ).…”

The GpsB files: the truth is out there

“…Straume et al . have also recently published an article in Molecular Microbiology that addresses PBPs, DivIVA and elongation regulators in the pneumococci (Straume et al ., ). Whilst some of the conclusions drawn by Straume et al .…”