We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
Sortase independent and dependent systems for acquisition of haem and haemoglobin in Listeria monocytogenes.
- Authors
Qiaobin Xiao; Xiaoxu Jiang; Moore, Kyle J.; Yi Shao; Hualiang Pi; Dubail, Iharilalao; Charbit, Alain; Newton, Salete M.; Klebba, Phillip E.
- Abstract
We studied three Fur-regulated systems of Listeria monocytogenes: the srtB region, that encodes sortase-anchored proteins and a putative ABC transporter, and the fhu and hup operons, that produce putative ABC transporters for ferric hydroxamates and haemin (Hn)/haemoglobin (Hb) respectively. Deletion of lmo2185 in the srtB region reduced listerial [Fe]-Hn transport, and purified Lmo2185 bound [Fe]-Hn ( K = 12 nM), leading to its designation as a n/b inding rotein ( hbp2) . Purified Hbp2 also acted as a haemophore, capturing and supplying Hn from the environment. Nevertheless, Hbp2 only functioned in [Fe]-Hn transport at external concentrations less than 50 nM: at higher Hn levels its uptake occurred with equivalent affinity and rate without Hbp2. Similarly, deletion of sortase A had no effect on ferric siderophore or Hn/Hb transport at any concentration, and the srtA-independence of listerial Hn/Hb uptake distinguished it from comparable systems of Staphylococcus aureus. In the cytoplasmic membrane, the Hup transporter was specific for Hn: its lipoprotein (HupD) only showed high affinity for the iron porphyrin ( K = 26 nM). Conversely, the FhuD lipoprotein encoded by the fhu operon had broad specificity: it bound both ferric siderophores and Hn, with the highest affinity for ferrioxamine B ( K = 123 nM). Deletions of Hup permease components hupD, hupG or hupDGC reduced Hn/Hb uptake, and complementation of ΔhupC and ΔhupG by chromosomal integration of hupC and hupG alleles on pPL2 restored growth promotion by Hn/Hb. However, ΔhupDGC did not completely eliminate [Fe]-Hn transport, implying the existence of another cytoplasmic membrane Hn transporter. The overall K of Hn uptake by wild-type strain EGD-e was 1 nM, and it occurred at similar rates ( V = 23 pmol 10 cells min) to those of ferric siderophore transporters. In the ΔhupDGC strain uptake occurred at a threefold lower rate ( V = 7 pmol 10 cells min). The results show that at low (< 50 nM) levels of Hn, SrtB-dependent peptidoglycan-anchored proteins (e.g. Hbp2) bind the porphyrin, and HupDGC or another transporter completes its uptake into the cytoplasm. However, at higher concentrations Hn uptake is SrtB-independent: peptidoglycan-anchored binding proteins are dispensable because HupDGC directly absorbs and internalizes Hn. Finally, ΔhupDGC increased the LD of L. monocytogenes 100-fold in the mouse infection model, reiterating the importance of this system in listerial virulence.
- Subjects
LISTERIA monocytogenes; HEME; HEMOGLOBINS; CARRIER proteins; MICROBIAL virulence
- Publication
Molecular Microbiology, 2011, Vol 80, Issue 6, p1581
- ISSN
0950-382X
- Publication type
Article
- DOI
10.1111/j.1365-2958.2011.07667.x