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Journal of Bacteriology, January 2009, p. 651-660, Vol. 191, No. 2
0021-9193/09/$08.00+0     doi:10.1128/JB.01083-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Mutagenesis of Region 4 of Sigma 28 from Chlamydia trachomatis Defines Determinants for Protein-Protein and Protein-DNA Interactions

Ziyu Hua,^1,2, Xiancai Rao,^1,2 Xiaogeng Feng,³ Xudong Luo,¹ Yanmei Liang,¹ and Li Shen^1,2*

Division of Infectious Diseases, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02118,¹ Department of Microbiology, Immunology, and Parasitology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112,² Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112³

Received 4 August 2008/ Accepted 24 October 2008

Transcription factor ²⁸ in Chlamydia trachomatis (²⁸_Ct) plays a role in the regulation of genes that are important for late-stage morphological differentiation. In vitro mutational and genetic screening in Salmonella enterica serovar Typhimurium was performed in order to identify mutants with mutations in region 4 of ²⁸_Ct that were defective in ²⁸-specific transcription. Specially, the previously undefined but important interactions between ²⁸_Ct region 4 and the flap domain of the RNA polymerase β subunit (β-flap) or the –35 element of the chlamydial hctB promoter were examined. Our results indicate that amino acid residues E206, Y214, and E222 of ²⁸_Ct contribute to an interaction with the β-flap when ²⁸_Ct associates with the core RNA polymerase. These residues function in contacts with the β-flap similarly to their counterpart residues in Escherichia coli ⁷⁰. Conversely, residue Q236 of ²⁸_Ct directly binds the chlamydial hctB –35 element. The conserved counterpart residue in E. coli ⁷⁰ has not been reported to interact with the –35 element of the ⁷⁰ promoter. Observed functional disparity between ²⁸_Ct and ⁷⁰ region 4 is consistent with their divergent properties in promoter recognition. This work provides new insight into understanding the molecular basis of gene regulation controlled by ²⁸_Ct in C. trachomatis.

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* Corresponding author. Mailing address: Department of Microbiology, Immunology and Parasitology, Louisiana State University Health Sciences Center, New Orleans, LA 70112. Phone: (504) 568-4076. Fax: (504) 568-2918. E-mail: lshen{at}lsuhsc.edu

Published ahead of print on 31 October 2008.

Present address: Children's Hospital, Chongqing University of Medical Sciences, Chongqing, China.

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Journal of Bacteriology, January 2009, p. 651-660, Vol. 191, No. 2
0021-9193/09/$08.00+0     doi:10.1128/JB.01083-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Rao, X., Deighan, P., Hua, Z., Hu, X., Wang, J., Luo, M., Wang, J., Liang, Y., Zhong, G., Hochschild, A., Shen, L. (2009). A regulator from Chlamydia trachomatis modulates the activity of RNA polymerase through direct interaction with the {beta} subunit and the primary {sigma} subunit. Genes Dev. 23: 1818-1829 [Abstract] [Full Text]