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<article article-type="research-article" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:mml="http://www.w3.org/1998/Math/MathML">
    <front>
        <journal-meta>
            <journal-id journal-id-type="publisher-id">TOBIOJ</journal-id>
            <journal-title>The Open Biology Journal</journal-title>
            <abbrev-journal-title abbrev-type="pubmed">Open Bio. J.</abbrev-journal-title>
            <issn pub-type="epub">1874-1967</issn>
            <publisher>
                <publisher-name>Bentham Open</publisher-name>
            </publisher>
        </journal-meta>
        <article-meta>
            <article-id pub-id-type="publisher-id">TOBIOJ-2-1</article-id>
            <article-id pub-id-type="doi">10.2174/1874196700902010001</article-id>
            <article-categories>
                <subj-group subj-group-type="heading">
                    <subject>Biology</subject>
                </subj-group>
            </article-categories>
            <title-group>
                <article-title>Salt Modulates Oligomerization Properties of hRad51 and hRad52 Proteins</article-title>
            </title-group>
            <contrib-group>
                <contrib>
                    <name>
                        <surname>Balakrishnan</surname>
                        <given-names>Kamakshi</given-names>
                    </name>
                    <xref ref-type="corresp" rid="cor2">&#x2020;</xref>
                </contrib>
                <contrib>
                    <name>
                        <surname>M. Krishnan</surname>
                        <given-names>Neeraja</given-names>
                    </name>
                    <xref ref-type="corresp" rid="cor2">&#x2020;</xref>
                </contrib>
                <contrib contrib-type="author" corresp="yes">
                    <name>
                        <surname>J. Rao</surname>
                        <given-names>Basuthkar</given-names>
                    </name>
                    <xref ref-type="corresp" rid="cor1">&#x002A;</xref>
                </contrib>
                <aff>Department of Biological Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai-400 005, India.</aff>
            </contrib-group>
            <author-notes>
                <corresp id="cor1">
                    <label>&#x002A;</label>Address correspondence to this author at the Department of Biological sciences, Tata Institute of Fundamental Research, Homi Bhabha Road,
Colaba, Mumbai-400 005, India; Tel: 091-22-22782606; Fax: 091-22-22804610; E-mail: <email xlink:href="bjrao@tifr.res.in">bjrao@tifr.res.in</email></corresp>
                <corresp id="cor2">
                    <label>&#x2020;</label>Equal Contribution</corresp>
            </author-notes>
            <pub-date pub-type="epub">
                <day>21</day>
                <month>1</month>
                <year>2009</year>
            </pub-date>
            <pub-date pub-type="collection">
                <year>2009</year>
            </pub-date>
            <volume>2</volume>
            <fpage>1</fpage>
            <lpage>9</lpage>
            <history>
                <date date-type="received">
                    <day>21</day>
                    <month>07</month>
                    <year>2008</year>
                </date>
                <date date-type="rev-recd">
                    <day>10</day>
                    <month>09</month>
                    <year>2008</year>
                </date>
                <date date-type="accepted">
                    <day>02</day>
                    <month>12</month>
                    <year>2008</year>
                </date>
            </history>
            <permissions>
                <copyright-statement>&#x00A9; 2008 J. Rao <italic>et al.</italic></copyright-statement>
                <copyright-year>2009</copyright-year>
                <copyright-holder>Basuthkar J. Rao</copyright-holder>
                <license license-type="open-access" xlink:href="https://creativecommons.org/licenses/by/4.0/legalcode">
                    <p>This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: (<uri xlink:href="https://creativecommons.org/licenses/by/4.0/legalcode">https://creativecommons.org/licenses/by/4.0/legalcode</uri>). This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.</p>
                </license>
            </permissions>
            <abstract>
                <p>Human Rad52 (hRad52) and Rad51 (hRad51) proteins are important components of homologous
recombination machinery involved in DNA double strand break repair. hRad52 subunits oligomerize to form rings, which
are further believed to stack one over another giving rise to higher order structures. Such structures bind the ends of
duplex DNA to bring about DNA end joining. hRad51 exists in the native state as oligomeric rings and monomerizes to
interact with the DNA. In our current study, we report disruption and solubilization of hRad52 aggregates and higher
order aggregation of hRad51 molecules at high salt (KCl) concentration. Computational analysis of the crystal structure
available for N-terminal 212 amino acids of hRad52 protein reveal a dense unique distribution of salt bridges, not only
between adjacent but also between penultimate subunit neighbors which perhaps contribute to stabilization of hRad52
oligomeric rings. Our results suggest that disruption of inter-subunit salt bridges and thereby perturbation of interaction
between individual monomers as the underlying mechanism for salt mediated monomerization of hRad52 protein. The
crystal structure of Rad51 on the other hand lacks such dense salt-bridge connectivity suggesting that salt-mediated
monomerization is a feature of proteins with dense salt-bridge networks. Salt brings together the hydrophobic surface
residues of hRad51 in a process termed as &#x201C;salting out&#x201D; resulting in aggregation of hRad51 molecules. Given the
functional relevance of oligomeric hRad52 and monomeric hRad51 in homologous recombination mediated repair, our
findings imply that salt regulates the oligomerization status of these repair proteins, and thereby, their functions
respectively.</p>
            </abstract>
            <kwd-group>
                <title>Keywords</title>
                <kwd>hRad52</kwd>
                <kwd>hRad51</kwd>
                <kwd>salt bridge</kwd>
                <kwd>monomerization</kwd>
                <kwd>aggregation</kwd>
                <kwd>oligomers</kwd>
                <kwd>KCl</kwd>
            </kwd-group>
        </article-meta>
    </front>
</article>
