Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 295, Issue 27, Pages 9171-9182Publisher
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.RA120.013994
Keywords
bacteria; peptidoglycan; cell surface enzyme; enzyme mechanism; serine; threonine protein kinase; dormancy; lytic transglycosylase; resuscitation-promoting factor (Rpf; ); LysM; LytM; cell wall; actinobacteria; enzyme
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Funding
- Canadian Institutes for Health Research [MOP-93635]
- Natural Sciences and Engineering Research Council [RGPIN 3215-11]
- Canada Graduate Scholarship
- Ontario Graduate Scholarships
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Bacterial dormancy can take many forms, including formation ofBacillusendospores,Streptomycesexospores, and metabolically latentMycobacteriumcells. In the actinobacteria, including the streptomycetes and mycobacteria, the rapid resuscitation from a dormant state requires the activities of a family of cell-wall lytic enzymes called resuscitation-promoting factors (Rpfs). Whether Rpf activity promotes resuscitation by generating peptidoglycan fragments (muropeptides) that function as signaling molecules for spore germination or by simply remodeling the dormant cell wall has been the subject of much debate. Here, to address this question, we used mutagenesis and peptidoglycan binding and cleavage assays to first gain broader insight into the biochemical function of diverse Rpf enzymes. We show that their LysM and LytM domains enhance Rpf enzyme activity; their LytM domain and, in some cases their LysM domain, also promoted peptidoglycan binding. We further demonstrate that the Rpfs function as endo-acting lytic transglycosylases, cleaving within the peptidoglycan backbone. We also found that unlike in other systems, Rpf activity in the streptomycetes is not correlated with peptidoglycan-responsive Ser/Thr kinases for cell signaling, and the germination ofrpfmutant strains could not be stimulated by the addition of known germinants. Collectively, these results suggest that inStreptomyces, Rpfs have a structural rather than signaling function during spore germination, and that in the actinobacteria, any signaling function associated with spore resuscitation requires the activity of additional yet to be identified enzymes.
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