Zinc fingers and thiol-disulfide oxidoreductase activities of chaperone DnaJ.
Chaperone DnaJ is a homodimer with each subunit containing 10 cysteine residues and two Zn(II) ions, which have been identified to form two zinc fingers, C(144)DVC(147)Zn(II)C(197)NKC(200) (Zn1) and C(161)PTC(164)Zn(II)C(183)PHC(186) (Zn2), with C(265) and C(323) in reduced form. Guanidine hydrochloride at 6.4 M destroys only Zn1, which does not reform after refolding. p-Hydroxymercuriphenylsulfonate acid, but not ethylenediaminetetraacetic acid (EDTA) even at high concentrations, can remove two Zn(II) ions from DnaJ, but only Zn2 can be reconstituted. After removal of Zn(II) ions, only C(144) and C(147) in Zn1 are oxidation-resistant, and the other six cysteines are easily oxidizable. DnaJ shows reductase activity and oxidase activity but little, if any, isomerase activity. The reductase activity is reversibly inhibited by EDTA. Zn2 is important for the enzymatic activity, and only -C(183)PHC(186)- among the four motifs of -CXXC- functions as the active site of the enzyme. A C-terminal (Q(181)-R(376)) fragment shows a zinc finger of C(183)PHC(186)Zn(II)C(197)NKC(200) and full enzymatic activity of DnaJ. The N-terminal half sequence (M(1)-Q(180)) and Zn1 are not required for the enzymatic activity but are important for the chaperone activity of DnaJ.
Tang
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National Laboratory of Biomacromolecules, Institute of Biophysics, Academia Sinica, 15 Datun Road, Beijing 100101, China.
Wang
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D007611:Aprotinin / Q000737:chemistry / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D002614:Chelating Agents / Q000378:metabolism; D004492:Edetic Acid / Q000378:metabolism; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction; D011487:Protein Conformation; D011489:Protein Denaturation; D011490:Protein Disulfide Reductase (Glutathione) / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D017510:Protein Folding; D012259:Ribonuclease, Pancreatic / Q000737:chemistry / Q000378:metabolism; D015032:Zinc / Q000378:metabolism; D016335:Zinc Fingers
D001426:Bacterial Proteins; D002614:Chelating Agents; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D007611:Aprotinin; D004492:Edetic Acid; D011490:Protein Disulfide Reductase (Glutathione); D012259:Ribonuclease, Pancreatic; D015032:Zinc