標題: Cloning and expression of human haptoglobin subunits in Escherichia coli: Delineation of a major antioxidant domain
作者: Lai, I. Hsiang
Tsai, Tsung I.
Lin, Hong Huei
Lai, Wei Yen
Mao, Simon J. T.
生醫工程研究所
Institute of Biomedical Engineering
關鍵字: human haptoglobin alpha and beta chains;cloning;mini-Hp fragment;antioxidant domain;monoclonal antibody;structure;circular dichroism
公開日期: 1-四月-2007
摘要: Human plasma haptoglobin (Hp) comprises alpha and beta subunits. The alpha subunit is heterogeneous in size, therefore isolation of Hp and its subunits is particularly difficult. Using Escherichia coli, we show that alpha 1, alpha 2, beta, and alpha 2 beta chain was abundantly expressed and primarily present in the inclusion bodies consisting of about 30% of the cell-lysate proteins. Each cloned subunit retained its immunoreactivity as confirmed using antibodies specific to alpha or beta chain. By circular dichroism, the structure of each expressed subunit was disordered as compared to the native Hp. The antioxidant activity was found to be associated with both alpha and beta chains when assessed by Cu2+-induced oxidation of low density lipoprotein (LDL). Of remarkable interest, the antioxidant activity of P chain was extremely potent and markedly greater than that of native Hp (3.5 x), alpha chain (10 x) and probucol (15 x). The latter is a clinically proved potent compound used for antioxidant therapy. The "unrestricted" structure of beta subunit may therefore render its availability for free-radical scavenge, which provides a utility for the future design of a "mini-Hp" in antioxidant therapy. It may also provide a new insight in understanding the mechanism involved in the antioxidant nature of Hp. (c) 2006 Elsevier Inc. All rights reserved.
URI: http://dx.doi.org/10.1016/j.pep.2006.09.012
http://hdl.handle.net/11536/10952
ISSN: 1046-5928
DOI: 10.1016/j.pep.2006.09.012
期刊: PROTEIN EXPRESSION AND PURIFICATION
Volume: 52
Issue: 2
起始頁: 356
結束頁: 362
顯示於類別:期刊論文


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