TY - JOUR T1 - Magnetite biomineralization in Magnetospirillum magneticum is regulated by a switch-like behavior in the HtrA protease MamE JF - bioRxiv DO - 10.1101/047555 SP - 047555 AU - David M. Hershey AU - Patrick J. Browne AU - Anthony T. Iavarone AU - Joan Teyra AU - Eun H. Lee AU - Sachdev S. Sidhu AU - Arash Komeili Y1 - 2016/01/01 UR - http://biorxiv.org/content/early/2016/06/07/047555.abstract N2 - Magnetotactic bacteria are aquatic organisms that produce subcellular magnetic particles in order to orient in the earth’s geomagnetic field. MamE, a predicted HtrA protease required to produce magnetite crystals in the magnetotactic bacterium Magnetospirillum magneticum AMB-1, was recently shown to promote the proteolytic processing of itself and two other biomineralization factors in vivo. Here, we have analyzed the in vivo processing patterns of three proteolytic targets and used this information to reconstitute proteolysis with a purified form of MamE in vitro. MamE cleaves a custom peptide substrate with positive cooperativity, and its auto-proteolysis can be stimulated with exogenous substrates or peptides that bind to either of its PDZ domains. A misregulated form of the protease that circumvents specific genetic requirements for proteolysis causes biomineralization defects, showing that proper regulation of its activity is required during magnetite biosynthesis in vivo. Our results represent the first reconstitution of MamE’s proteolytic activity and show that its behavior is consistent with the previously proposed checkpoint model for biomineralization. ER -