Oxidative folding of hirudin in human serum.
Human serum contains factors that promote oxidative folding of disulphide proteins. We demonstrate this here using hirudin as a model. Hirudin is a leech-derived thrombin-specific inhibitor containing 65 amino acids and three disulphide bonds. Oxidative folding of hirudin in human serum is shown to involve an initial phase of rapid disulphide formation (oxidation) to form the scrambled isomers as intermediates. This is followed by the stage of slow disulphide shuffling of scrambled isomers to attain the native hirudin. The kinetics of regenerating the native hirudin depend on the concentrations of both hirudin and human serum. Quantitative regeneration of native hirudin in undiluted human serum can be completed within 48 h, without any redox supplement. These results cannot be adequately explained by the existing oxidized thiol agents in human serum or the macromolecular crowding effect, and therefore indicate that human serum may contain yet to be identified potent oxidase(s) for assisting protein folding.
Chang
Jui-Yoa
JY
Research Center for Protein Chemistry, Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases, The University of Texas, Houston, TX 77030, USA. Rowen.Chang@uth.tmc.edu
Lu
Bao-Yun
BY
Lai
Por-Hsiung
PH
D000818:Animals; D006629:Hirudins / Q000097:blood* / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D007865:Leeches / Q000737:chemistry*; D010084:Oxidation-Reduction; D017510:Protein Folding; D044967:Serum
D006629:Hirudins