CotC-CotU heterodimerization during assembly of the Bacillus subtilis spore coat

Dipartimento di Biologia Strutturale e Funzionale, Università Federico II, Napoli, Italy; Departmento de Biologia Vegetal, Universidade de Lisboa, Lisboa, Portugal ; Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Avenida da República, Apartado 127 2781-901 Oeiras, Portugal

^* To whom correspondence should be addressed. Email: ericca{at}unina.it.

	Abstract

We report evidence that CotC and CotU, two previously identified components of the Bacillus subtilis spore coat, are produced coincidently 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 only occurs in B. subtilis. Monomeric forms of both CotU and CotC fail to be assembled at the surface of the developing spore, and accumulate in the mother cell compartment of cells mutant for cotE. In contrast, neither CotU nor CotC accumulate in the mother cell compartment of cells mutant for cotH. The 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.