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Subcellular localization of a sporulation membrane protein is achieved through a network of interactions along and across the septum
Author(s) -
Doan Thierry,
Marquis Kathleen A.,
Rudner David Z.
Publication year - 2005
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2005.04501.x
Subject(s) - biology , microbiology and biotechnology , cell , membrane protein , bacillus subtilis , morphogenesis , cell membrane , protein–protein interaction , membrane , biochemistry , genetics , gene , bacteria
Summary During the process of spore formation in Bacillus subtilis many membrane proteins localize to the sporulation septum where they play key roles in morphogenesis and cell‐cell signalling. However, the mechanism by which these proteins are anchored at this site is not understood. In this report we have defined the localization requirements for the mother‐cell membrane protein SpoIVFA, which anchors a signalling complex in the septal membrane on the mother cell side. We have identified five proteins (SpoIID, SpoIIP, SpoIIM, BofA and SpoIIIAH) synthesized in the mother cell under the control of σ E and one protein (SpoIIQ) synthesized in the forespore under the control of σ F that are all required for the proper localization of SpoIVFA. Surprisingly, these proteins appear to have complementary and overlapping anchoring roles suggesting that SpoIVFA is localized in the septal membrane through a web of protein interactions. Furthermore, we demonstrate a direct biochemical interaction between the extracellular domains of two of the proteins required to anchor SpoIVFA: the forespore protein SpoIIQ and the mother‐cell protein SpoIIIAH. This result supports the idea that the web of interactions that anchors SpoIVFA is itself held in the septal membrane through a zipper‐like interaction across the sporulation septum. Importantly, our results suggest that a second mechanism independent of forespore proteins participates in anchoring SpoIVFA. Finally, we show that the dynamic localization of SpoIIQ in the forespore is impaired in the absence of SpoIVFA but not SpoIIIAH. Thus, a complex web of interactions among mother cell and forespore proteins is responsible for static and dynamic protein localization in both compartments of the sporangium. We envision that this proposed network is involved in anchoring other sporulation proteins in the septum and that protein networks with overlapping anchoring capacity is a feature of protein localization in all bacteria.