Divalent cations stabilize GroEL under conditions of oxidative stress |
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| Authors: | Melkani Girish C Sielaff Robin L Zardeneta Gustavo Mendoza Jose A |
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| Affiliation: | a Department of Chemistry and Biochemistry, California State University, 333 South Twin Oaks Valley Road, San Marcos, CA 92096-0001, USA
b Department of Biology and Earth Sciences, Adams State College, Alamosa, CO 81102, USA |
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| Abstract: | The divalent cations Mg2+, Mn2+, Zn2+, Ca2+, and Ni2+ were found to protect against proteolysis a form of GroEL (ox-GroEL) prepared by exposing GroEL for 16 h to 6 mM hydrogen peroxide (H2O2). K+ and other monovalent cations did not have any effect. Divalent cations also induced a conformational change of ox-GroEL that led to the decrease of its large exposed hydrophobic surfaces (exposed with H2O2). Ox-GroEL incubated with a divalent cation behaved like N-GroEL in that it could transiently interact with H2O2-inactivated rhodanese (ox-rhodanese), whereas ox-GroEL alone could strongly interact with ox-rhodanese. Although, ox-GroEL incubated with a divalent cation could not recover the ATPase activity (66%) lost with H2O2, it could facilitate the reactivation of ox-rhodanese (>86% of active rhodanese recovered), without requiring ATP or the co-chaperonin, GroES. This is the first report to demonstrate a role for the divalent cations on the structure and function of ox-GroEL. |
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| Keywords: | ATP, adenosine triphosphate bisANS, 1,1&prime -bis(4-anilino) naphthalene-5,5&prime -disulfonic acid, dipotassium salt βME, β-mercaptoethanol PMSF, phenyl methyl sulphonyl fluoride SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis |
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