title: Divalent cations stabilize GroEL under conditions of oxidative stress.
abstract: The divalent cations Mg(2+), Mn(2+), Zn(2+), Ca(2+), and Ni(2+) were found to protect against proteolysis a form of GroEL (ox-GroEL) prepared by exposing GroEL for 16h to 6mM hydrogen peroxide (H(2)O(2)). 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 H(2)O(2)). Ox-GroEL incubated with a divalent cation behaved like N-GroEL in that it could transiently interact with H(2)O(2)-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 H(2)O(2), 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.
authors.affiliation: Department of Chemistry and Biochemistry, California State University, 333 South Twin Oaks Valley Road, San Marcos, CA 92096-0001, USA.
authors.forename: Girish C
authors.initials: GC
authors.lastname: Melkani
authors.forename: Robin L
authors.initials: RL
authors.lastname: Sielaff
authors.forename: Gustavo
authors.initials: G
authors.lastname: Zardeneta
authors.forename: Jose A
authors.initials: JA
authors.lastname: Mendoza
mesh_terms: D002412:Cations; D018834:Chaperonin 60 / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry*; D018384:Oxidative Stress; D010100:Oxygen / Q000737:chemistry*
chemical_list: D002412:Cations; D018834:Chaperonin 60; D006861:Hydrogen Peroxide; D010100:Oxygen