title: GroEL interacts transiently with oxidatively inactivated rhodanese facilitating its reactivation.
abstract: When the enzyme rhodanese was inactivated with hydrogen peroxide (H(2)O(2)), it underwent significant conformational changes, leading to an increased exposure of hydrophobic surfaces. Thus, this protein seemed to be an ideal substrate for GroEL, since GroEL uses hydrophobic interactions to bind to its substrate polypeptides. Here, we report on the facilitated reactivation (86%) of H(2)O(2)-inactivated rhodanese by GroEL alone. Reactivation by GroEL required a reductant and the enzyme substrate, but not GroES or ATP. Further, we found that GroEL interacted weakly and/or transiently with H(2)O(2)-inactivated rhodanese. A strong interaction with rhodanese was obtained when the enzyme was pre-incubated with urea, indicating that exposure of hydrophobic surfaces alone on oxidized rhodanese was not sufficient for the formation of a strong complex and that a more unfolded structure of rhodanese was required to interact strongly with GroEL. Unlike prior studies that involved denaturation of rhodanese through chemical or thermal means, we have clearly shown that GroEL can function as a molecular chaperone in the reactivation of an oxidatively inactivated protein. Additionally, the mechanism for the GroEL-facilitated reactivation of rhodanese shown here appears to be different than that for the chaperonin-assisted folding of chemically unfolded polypeptides in which a nucleotide and sometimes GroES is required.
authors.affiliation: Department of Chemistry and Biochemistry, California State University at San Marcos, 92096-0001, USA.
authors.forename: Girish C
authors.initials: GC
authors.lastname: Melkani
authors.forename: Gustavo
authors.initials: G
authors.lastname: Zardeneta
authors.forename: Jose A
authors.initials: JA
authors.lastname: Mendoza
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002417:Cattle; D018835:Chaperonin 10 / Q000378:metabolism; D018834:Chaperonin 60 / Q000378:metabolism*; D018833:Chaperonins / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D008099:Liver / Q000201:enzymology; D010100:Oxygen / Q000378:metabolism*; D011485:Protein Binding; D013050:Spectrometry, Fluorescence; D013884:Thiosulfate Sulfurtransferase / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D018835:Chaperonin 10; D018834:Chaperonin 60; D000255:Adenosine Triphosphate; D006861:Hydrogen Peroxide; D013884:Thiosulfate Sulfurtransferase; D018833:Chaperonins; D010100:Oxygen