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Journal of Bacteriology, September 2008, p. 5879-5889, Vol. 190, No. 17
0021-9193/08/$08.00+0     doi:10.1128/JB.00685-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Function and Redundancy of the Chaplin Cell Surface Proteins in Aerial Hypha Formation, Rodlet Assembly, and Viability in Streptomyces coelicolor

Department of Biology and Institute for Infectious Disease Research, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4K1, Canada,¹ John Innes Centre, Colney, Norwich NR4 7UH, United Kingdom²

Received 15 May 2008/ Accepted 20 June 2008

The chaplins are a family of eight secreted proteins that are critical for raising aerial hyphae in Streptomyces coelicolor. These eight chaplins can be separated into two main groups: the long chaplins (ChpA to -C) and the short chaplins (ChpD to -H). The short chaplins can be further subdivided on the basis of their abilities to form intramolecular disulfide bonds: ChpD, -F, -G, and -H contain two Cys residues, while ChpE has none. A "minimal chaplin strain" containing only chpC, chpE, and chpH was constructed and was found to raise a substantial aerial mycelium. This strain was used to examine the roles of specific chaplins. Within this strain, the Cys-containing ChpH was identified as the major polymerization unit contributing to aerial hypha formation and assembly of an intricate rodlet ultrastructure on the aerial surfaces, and the two Cys residues were determined to be critical for its function. ChpC augmented aerial hypha formation and rodlet assembly, likely by anchoring the short chaplins to the cell surface, while ChpE was essential for the viability of wild-type S. coelicolor. Interestingly, the lethal effects of a chpE null mutation could be suppressed by the loss of the other chaplins, the inactivation of the twin arginine translocation (Tat) secretion pathway, or the loss of the rodlins.

Published ahead of print on 17 June 2008.