title: Protein complexes and proteolytic activation of the cell wall hydrolase RipA regulate septal resolution in mycobacteria.
abstract: Peptidoglycan hydrolases are a double-edged sword. They are required for normal cell division, but when dysregulated can become autolysins lethal to bacteria. How bacteria ensure that peptidoglycan hydrolases function only in the correct spatial and temporal context remains largely unknown. Here, we demonstrate that dysregulation converts the essential mycobacterial peptidoglycan hydrolase RipA to an autolysin that compromises cellular structural integrity. We find that mycobacteria control RipA activity through two interconnected levels of regulation in vivo-protein interactions coordinate PG hydrolysis, while proteolysis is necessary for RipA enzymatic activity. Dysregulation of RipA protein complexes by treatment with a peptidoglycan synthase inhibitor leads to excessive RipA activity and impairment of correct morphology. Furthermore, expression of a RipA dominant negative mutant or of differentially processed RipA homologues reveals that RipA is produced as a zymogen, requiring proteolytic processing for activity. The amount of RipA processing differs between fast-growing and slow-growing mycobacteria and correlates with the requirement for peptidoglycan hydrolase activity in these species. Together, the complex picture of RipA regulation is a part of a growing paradigm for careful control of cell wall hydrolysis by bacteria during growth, and may represent a novel target for chemotherapy development.
authors.affiliation: Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts, United States of America.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Chao
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Kieser
authors.forename: Shoko
authors.initials: S
authors.lastname: Minami
authors.forename: Daniela
authors.initials: D
authors.lastname: Mavrici
authors.forename: Bree B
authors.initials: BB
authors.lastname: Aldridge
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Fortune
authors.forename: Tom
authors.initials: T
authors.lastname: Alber
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Rubin
mesh_terms: D002455:Cell Division; D002473:Cell Wall / Q000201:enzymology*; D004269:DNA, Bacterial / Q000032:analysis; D004791:Enzyme Inhibitors / Q000494:pharmacology; D009097:Multienzyme Complexes / Q000378:metabolism*; D020102:Mycobacterium smegmatis / Q000201:enzymology* / Q000235:genetics / Q000648:ultrastructure; D009238:N-Acetylmuramoyl-L-alanine Amidase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D059748:Proteolysis
chemical_list: D004269:DNA, Bacterial; D004791:Enzyme Inhibitors; D009097:Multienzyme Complexes; D009238:N-Acetylmuramoyl-L-alanine Amidase