Structural Analysis of the cl-Par-4 Tumor Suppressor as a Function of Ionic Environment
Prostate apoptosis response-4 (Par-4) is a proapoptotic tumor suppressor protein that has been linked to a large number of cancers. This 38 kilodalton (kDa) protein has been shown to be predominantly intrinsically disordered in vitro. In vivo, Par-4 is cleaved by caspase-3 at Asp-131 to generate the...
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| Format: | Article |
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MDPI AG
2021-03-01
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| Series: | Biomolecules |
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| Online Access: | https://www.mdpi.com/2218-273X/11/3/386 |
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| author | Krishna K. Raut Komala Ponniah Steven M. Pascal |
| author_facet | Krishna K. Raut Komala Ponniah Steven M. Pascal |
| author_sort | Krishna K. Raut |
| collection | DOAJ |
| description | Prostate apoptosis response-4 (Par-4) is a proapoptotic tumor suppressor protein that has been linked to a large number of cancers. This 38 kilodalton (kDa) protein has been shown to be predominantly intrinsically disordered in vitro. In vivo, Par-4 is cleaved by caspase-3 at Asp-131 to generate the 25 kDa functionally active cleaved Par-4 protein (cl-Par-4) that inhibits NF-κB-mediated cell survival pathways and causes selective apoptosis in tumor cells. Here, we have employed circular dichroism (CD) spectroscopy and dynamic light scattering (DLS) to assess the effects of various monovalent and divalent salts upon the conformation of cl-Par-4 in vitro. We have previously shown that high levels of sodium can induce the cl-Par-4 fragment to form highly compact, highly helical tetramers in vitro. Spectral characteristics suggest that most or at least much of the helical content in these tetramers are non-coiled coils. Here, we have shown that potassium produces a similar effect as was previously reported for sodium and that magnesium salts also produce a similar conformation effect, but at an approximately five times lower ionic concentration. We have also shown that anion identity has far less influence than does cation identity. The degree of helicity induced by each of these salts suggests that the “Selective for Apoptosis in Cancer cells” (SAC) domain—the region of Par-4 that is most indispensable for its apoptotic function—is likely to be helical in cl-Par-4 under the studied high salt conditions. Furthermore, we have shown that under medium-strength ionic conditions, a combination of high molecular weight aggregates and smaller particles form and that the smaller particles are also highly helical, resembling at least in secondary structure, the tetramers found at high salt. |
| first_indexed | 2024-03-09T05:19:41Z |
| format | Article |
| id | doaj.art-e53cae6fed574674856bf4186be217f5 |
| institution | Directory Open Access Journal |
| issn | 2218-273X |
| language | English |
| last_indexed | 2024-03-09T05:19:41Z |
| publishDate | 2021-03-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Biomolecules |
| spelling | doaj.art-e53cae6fed574674856bf4186be217f52023-12-03T12:42:38ZengMDPI AGBiomolecules2218-273X2021-03-0111338610.3390/biom11030386Structural Analysis of the cl-Par-4 Tumor Suppressor as a Function of Ionic EnvironmentKrishna K. Raut0Komala Ponniah1Steven M. Pascal2Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA 23529, USADepartment of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA 23529, USADepartment of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA 23529, USAProstate apoptosis response-4 (Par-4) is a proapoptotic tumor suppressor protein that has been linked to a large number of cancers. This 38 kilodalton (kDa) protein has been shown to be predominantly intrinsically disordered in vitro. In vivo, Par-4 is cleaved by caspase-3 at Asp-131 to generate the 25 kDa functionally active cleaved Par-4 protein (cl-Par-4) that inhibits NF-κB-mediated cell survival pathways and causes selective apoptosis in tumor cells. Here, we have employed circular dichroism (CD) spectroscopy and dynamic light scattering (DLS) to assess the effects of various monovalent and divalent salts upon the conformation of cl-Par-4 in vitro. We have previously shown that high levels of sodium can induce the cl-Par-4 fragment to form highly compact, highly helical tetramers in vitro. Spectral characteristics suggest that most or at least much of the helical content in these tetramers are non-coiled coils. Here, we have shown that potassium produces a similar effect as was previously reported for sodium and that magnesium salts also produce a similar conformation effect, but at an approximately five times lower ionic concentration. We have also shown that anion identity has far less influence than does cation identity. The degree of helicity induced by each of these salts suggests that the “Selective for Apoptosis in Cancer cells” (SAC) domain—the region of Par-4 that is most indispensable for its apoptotic function—is likely to be helical in cl-Par-4 under the studied high salt conditions. Furthermore, we have shown that under medium-strength ionic conditions, a combination of high molecular weight aggregates and smaller particles form and that the smaller particles are also highly helical, resembling at least in secondary structure, the tetramers found at high salt.https://www.mdpi.com/2218-273X/11/3/386intrinsically disordered protein (IDP)prostate apoptosis response-4 (Par-4)tumor suppressorcircular dichroism (CD) spectroscopydynamic light scattering (DLS)aggregation |
| spellingShingle | Krishna K. Raut Komala Ponniah Steven M. Pascal Structural Analysis of the cl-Par-4 Tumor Suppressor as a Function of Ionic Environment Biomolecules intrinsically disordered protein (IDP) prostate apoptosis response-4 (Par-4) tumor suppressor circular dichroism (CD) spectroscopy dynamic light scattering (DLS) aggregation |
| title | Structural Analysis of the cl-Par-4 Tumor Suppressor as a Function of Ionic Environment |
| title_full | Structural Analysis of the cl-Par-4 Tumor Suppressor as a Function of Ionic Environment |
| title_fullStr | Structural Analysis of the cl-Par-4 Tumor Suppressor as a Function of Ionic Environment |
| title_full_unstemmed | Structural Analysis of the cl-Par-4 Tumor Suppressor as a Function of Ionic Environment |
| title_short | Structural Analysis of the cl-Par-4 Tumor Suppressor as a Function of Ionic Environment |
| title_sort | structural analysis of the cl par 4 tumor suppressor as a function of ionic environment |
| topic | intrinsically disordered protein (IDP) prostate apoptosis response-4 (Par-4) tumor suppressor circular dichroism (CD) spectroscopy dynamic light scattering (DLS) aggregation |
| url | https://www.mdpi.com/2218-273X/11/3/386 |
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