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. Author manuscript; available in PMC: 2014 Dec 1.
Published in final edited form as: Biochim Biophys Acta. 2013 Dec;1828(12):2873–2885. doi: 10.1016/j.bbamem.2013.03.032

Figure 3.

Figure 3

A model for ATP transport and accumulation during B. subtilis sporulation, and localization of the SpoIVFB complex with channel and engulfment complexes. A complex of SpoIIM, SpoIIP, and SpoIID proteins (red) interacts with the cell wall and causes the mother cell membrane to engulf the forespore (top left). During engulfment, channels (green) composed of SpoIIQ expressed in the forespore and SpoIIIA proteins expressed in the mother cell are formed. The channels span the intermembrane space and have been proposed to allow small molecules like ATP to move from the mother cell into the forespore. Upon completion of engulfment, the channels undergo reorganization and some components are degraded (top right). We propose that the ATP concentration rises in the mother cell and this is sensed by the CBS domain of SpoIVFB. SpoIVFA facilitates assembly of SpoIVFB with its inhibitor BofA and localizes the complex (magenta) to foci that during engulfment include the channel and engulfment complexes (bottom part), although whether SpoIVFA interacts directly with a protein(s) in the other complexes or interacts indirectly is unknown (dashed arrows).