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Originally published In Press as doi:10.1074/jbc.M409253200 on November 9, 2004
J. Biol. Chem., Vol. 280, Issue 2, 1209-1216, January 14, 2005
Calcium-binding Crystallins from Yersinia pestis
CHARACTERIZATION OF TWO SINGLE  -CRYSTALLIN DOMAINS OF A PUTATIVE EXPORTED PROTEIN*
Maroor K. Jobby and
Yogendra Sharma
From the
Center for Cellular and Molecular Biology, Uppal Road, Hyderabad-500007, India
 -Crystallin is a superfamily with diverse members from vertebrate lens to microbes. However, not many members have been identified and studied. Here, we report the identification of a putative exported protein from Yersinia pestis as a member of the  -crystallin superfamily. Even though calcium has been known to play an important role in the physiology and virulence of the Yersinia genus, calcium-binding proteins have not yet been identified. We have studied the calcium-binding properties of two of the three crystallin domains present in this putative exported protein designated "Yersinia crystallin." These two domains (D1 and D2) have unique AA and BB types of arrangement of their Greek key motifs unlike the domains of other members of the  -crystallin superfamily, which are either AB or BA types. These domains bind two calcium ions with low and high affinity-binding sites. We showed their calcium-binding properties using various probes for calcium and the effect of calcium on their secondary and tertiary structures. Although both domains bind calcium, D1 underwent drastic changes in secondary and tertiary structure and hydrodynamic volume upon calcium binding. Domain D1, which is intrinsically unstructured in the apo form, requires calcium for the typical  -crystallin fold. Calcium exerted an extrinsic stabilization effect on domain D1 but not on D2, which is also largely unstructured. We suggest that this protein might be involved in calcium-dependent processes, such as stress response or physiology in the Yersinia genus, similar to its microbial relatives and mammalian lens crystallins.
Received for publication, August 12, 2004
, and in revised form, October 25, 2004.
* This work was supported by a Third World Academy of Science (TWAS, Italy) Research Grant 03-231 RG/BIO/AS. 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, Government of India.
To whom correspondence should be addressed. Fax: 91-40-27160591; E-mail: yogendra{at}ccmb.res.in.

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Copyright © 2005 by the American Society for Biochemistry and Molecular Biology.
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