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Functional analysis of the competence transcription factor ComK of Bacillus subtilis by characterization of truncation variants

Kim A. Susanna^1,

Leendert W. Hamoen^1,

¹ Department of Genetics, University of Groningen, NL-9751 NN Haren, The Netherlands
² Laboratory of Biophysical Chemistry, Department of Chemistry, University of Groningen, NL-9747 AG Groningen, The Netherlands

Correspondence
Oscar P. Kuipers
O.P.Kuipers{at}rug.nl

The competence transcription factor ComK is the master regulator of competence development in Bacillus subtilis. In the regulatory pathway, ComK is involved in different interactions: (i) protein–DNA interactions to stimulate transcription of ComK-dependent genes and (ii) protein–protein interactions, divided into interactions with other proteins and interactions between ComK proteins involving oligomerization. The fact that ComK displays different types of interactions suggests the presence of specific, distinct domains in the protein. This paper describes a search for functional domains, by constructing ComK truncation variants, which were tested for DNA binding, oligomerization and transcription activation. Truncations at the C-terminal end of ComK demonstrated the requirement of this part for transcription activation, but not for DNA binding. The C-terminal region is probably involved in oligomerization of ComK-dimers into tetramers. Surprisingly, a ComK truncation variant lacking 9 aa from the N-terminal end (N9ComK) showed higher transcription activation than wild-type ComK, when expressed in Lactococcus lactis. However, in B. subtilis, transcription activation by N9ComK was twofold lower than that by wild-type ComK, resulting from a five- to sixfold lower protein level of ComKN9. Thus, relatively, N9ComK is more active in transcription activation than wild-type ComK. These results suggest that the presence of this N-terminal extension on ComK is a trade-off between high transcription activation and a thus far unidentified role in regulation of ComK.

Present address: Department of Pharmaceutical Biosciences, School of Pharmacy, University of Oslo, PO Box 1068 Blindern, 0316 Oslo, Norway.

Present address: Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK.

This article has been cited by other articles:

				K. A. Susanna, A. M. Mironczuk, W. K. Smits, L. W. Hamoen, and O. P. Kuipers A Single, Specific Thymine Mutation in the ComK-Binding Site Severely Decreases Binding and Transcription Activation by the Competence Transcription Factor ComK of Bacillus subtilis J. Bacteriol., July 1, 2007; 189(13): 4718 - 4728. [Abstract] [Full Text] [PDF]