Engulfment during sporulation in Bacillus subtilis is governed by a multi-protein complex containing tandemly acting autolysins.
The conversion of a growing cell into an endospore in Bacillus subtilis involves a phagocytic-like process in which the developing spore (the forespore) is wholly engulfed by the adjacent mother cell. A prerequisite for engulfment is the removal of peptidoglycan from the septum that separates the forespore from the mother cell, a process that depends on the autolysin SpoIID and two proteins of unknown function, SpoIIM and SpoIIP. Here we present evidence that SpoIIP is also an autolysin, that it acts in tandem with SpoIID, and that all three proteins are in a complex with each other. We further show that the members of the complex exhibit a hierarchical relationship in which SpoIIM is responsible for localization to the septal membrane, SpoIIP localizes to the septal membrane by interacting with SpoIIM, and SpoIID, in turn, localizes by interacting with SpoIIP. Finally, we show that localization of SpoIIM depends on a fourth protein SpoIIB, raising the possibility that the complex contains an additional component and creating an overall hierarchy of the form: SpoIIB-->SpoIIM-->SpoIIP-->SpoIID.
Chastanet
Arnaud
A
Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
Losick
Richard
R
D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000378:metabolism / Q000502:physiology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009238:N-Acetylmuramoyl-L-alanine Amidase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism*; D013171:Spores, Bacterial / Q000502:physiology; D013347:Subcellular Fractions / Q000378:metabolism
D001426:Bacterial Proteins; D011993:Recombinant Fusion Proteins; C030069:spore-specific proteins, Bacillus; D049452:Green Fluorescent Proteins; D009238:N-Acetylmuramoyl-L-alanine Amidase