Expression of the hemolysin operon in Escherichia coli is modulated by a nucleoid-protein complex that includes the proteins Hha and H-NS |
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Authors: | Nieto J M Madrid C Prenafeta A Miquelay E Balsalobre C Carrascal M Juárez A |
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Institution: | (1) Departament de Microbiologia. Universitat de Barcelona, Avda. Diagonal, 645, 08028 Barcelona, Spain Tel.: +34 93 4021487; Fax: +34 93 4110592 E-mail: juarez@porthos.bio.ub.es, ES;(2) Espectrometría de Masas Estructural y Biológica, Departamento Bioanalítica Médica, IIBB, IDIBARS, CSIC, Jordi Girona, 18-26, 08034 Barcelona, Spain, ES |
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Abstract: | The Escherichia coli protein Hha is a temperature- and osmolarity-dependent modulator of the expression of the hemolysin operon. The Hha protein
was purified and its DNA-binding properties analyzed. Hha binds in a non-specific manner throughout the upstream regulatory
region of the hemolysin operon in the recombinant hemolytic plasmid pANN202-312. A search for interacting proteins revealed
that Hha interacts with H-NS. DNA-binding studies showed that, in vitro, Hha and H-NS together form a complex with DNA that
differs from those formed with either protein alone. These data, together with the effects of hha and hns mutations on the expression of the hemolysin genes, suggest that in vivo H-NS and Hha form a nucleoid-protein complex that
accounts for the thermo-osmotic regulation of the hemolysin operon in E. coli.
Received. 18 October 1999 / Accepted: 21 December 1999 |
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Keywords: | Hha H-NS Protein-protein interaction Protein-DNA interaction Hemolysin |
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