CotC-CotU Heterodimerization during Assembly of the Bacillus subtilis Spore Coat

Abstract

We report evidence that CotC and CotU, two previously identified components of the Bacillus subtilis spore coat, are produced concurrently in the mother cell chamber of the sporulating cell under the control of K and GerE and immediately assembled around the forming spore. In the coat, the two proteins interact to form a coat component of 23 kDa. The CotU-CotC interaction was not detected in two heterologous hosts, suggesting that it occurs only in B. subtilis. Monomeric forms of both CotU and CotC failed to be assembled at the surface of the developing spore and accumulated in the mother cell compartment of cells mutant for cotE. In contrast, neither CotU nor CotC accumulated in the mother cell compartment of cells mutant for cotH. These results suggest that CotH is required to protect both CotU and CotC in the mother cell compartment of the sporangium and that CotE is needed to allow their assembly and subsequent interaction at the spore surface.

Expression of yeeK during Bacillus subtilis Sporulation and Localization of YeeK to the Inner Spore Coat using Fluorescence Microscopy

“…We speculate that YeeK promotes the survival of spores in certain environments. Recent studies focused on interactions of the spore coat with other proteins (8,22,23). In addition, we remain interested in interactions of spore coat proteins and we would like to further investigate the role of YabG.…”

CotE Binds to CotC and CotU and Mediates Their Interaction during Spore Coat Formation in Bacillus subtilis

“…The two proteins, which share an almost identical N terminus and a less conserved C terminus, interact, originating the formation of a heterodimer of 23 kDa (10). Heterodimer formation most likely requires a B. subtilis-specific factor since it does not occur in Escherichia coli or Saccharomyces cerevisiae (10). CotC and CotU are synthesized in the mother cell compartment of the sporulating cell but do not accumulate there since they are immediately assembled around the forming spore (10).…”

“…Evidence of a direct interaction between CotE and another coat component has never been provided. We addressed this issue by using as a model two coat components, CotC and CotU, known to be controlled by CotE and to form a heterodimer (10,28).…”

“…Heterodimer formation most likely requires a B. subtilis-specific factor since it does not occur in Escherichia coli or Saccharomyces cerevisiae (10). CotC and CotU are synthesized in the mother cell compartment of the sporulating cell but do not accumulate there since they are immediately assembled around the forming spore (10). In a strain carrying a cotE-null mutation, CotC and CotU, together with all other outer coat components, do not assemble around the forming spore (10).…”

A Novel Small Protein ofBacillus subtilisInvolved in Spore Germination and Spore Coat Assembly

“…CotH also has a role in the stabilization of CotC and CotU in the mother cell cytoplasm during sporulation. 45,46) Although the CotC and CotU corresponding proteins could not be distinguished by Tricine SDS-PAGE, these proteins are defective in the cotH mutant spores.…”