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J. Biol. Chem., Vol. 280, Issue 20, 19641-19648, May 20, 2005

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Purified Recombinant Hypothetical Protein Coded by Open Reading Frame Rv1885c of Mycobacterium tuberculosis Exhibits a Monofunctional AroQ Class of Periplasmic Chorismate Mutase Activity^*

Prachee Prakash, Bandi Aruna, Abhijit A. Sardesai¶, and Seyed E. Hasnain||**

From the Laboratories of Molecular and Cellular Biology and ^¶Bacterial Genetics, Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500076, India and ^||Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India

Naturally occurring variants of the enzyme chorismate mutase are known to exist that exhibit diversity in enzyme structure, regulatory properties, and association with other proteins. Chorismate mutase was not annotated in the initial genome sequence of Mycobacterium tuberculosis (Mtb) because of low sequence similarity between known chorismate mutases. Recombinant protein coded by open reading frame Rv1885c of Mtb exhibited chorismate mutase activity in vitro. Biochemical and biophysical characterization of the recombinant protein suggests its resemblance to the AroQ class of chorismate mutases, prototype examples of which include the Escherichia coli and yeast chorismate mutases. We also demonstrate that unlike the corresponding proteins of E. coli, Mtb chorismate mutase does not have any associated prephenate dehydratase or dehydrogenase activity, indicating its monofunctional nature. The Rv1885c-encoded chorismate mutase showed allosteric regulation by pathway-specific as well as cross-pathway-specific ligands, as evident from proteolytic cleavage protection and enzyme assays. The predicted N-terminal signal sequence of Mtb chorismate mutase was capable of functioning as one in E. coli, suggesting that Mtb chorismate mutase belongs to the AroQ class of chorismate mutases. It was evident that Rv1885c may not be the only enzyme with chorismate mutase enzyme function within Mtb, based on our observation of the presence of chorismate mutase activity displayed by another hypothetical protein coded by open reading frame Rv0948c, a novel instance of the existence of two monofunctional chorismate mutases ever reported in any pathogenic bacterium.

Received for publication, November 18, 2004 , and in revised form, February 28, 2005.

^* This work was supported by grants from the Department of Biotechnology, Government of India. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Recipient of a Senior Research Fellowship from the Council of Scientific and Industrial Research.

^** To whom correspondence should be addressed: Laboratory of Molecular and Cellular Biology, Centre for DNA Fingerprinting and Diagnostics, Nacharam, Hyderabad, 500076, India. Tel.: 91-40-27155604; Fax: 91-40-27155610; E-mail: hasnain{at}cdfd.org.in.

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