標題: Epitope mapping of a monoclonal antibody specific to bovine dry milk - Involvement of residues 66-76 of strand D in thermal denatured beta-lactoglobulin
作者: Song, CY
Chen, WL
Yang, MC
Huang, JP
Mao, SJT
生物科技學系
Department of Biological Science and Technology
公開日期: 4-Feb-2005
摘要: beta-Lactoglobulin (beta-LG) is a bovine milk protein sensitive to thermal denaturation. Previously, we demonstrated that such structural change can be detected by a monoclonal antibody (mAb) specific to denatured beta-LG. In the present study, we show a dramatic increase in beta-LG immunoreactivity when heating raw milk between 70 and 80 degreesC. To map out the specific epitope of beta-LG recognized by this mAb, we used a combined strategy including tryptic and CNBr fragments, chemical modifications (acetylation and carboxymethylation), peptide array containing in situ synthesized peptides, and a synthetic soluble peptide for immunoassays. The antigenic determinant we defined was exactly located within the D strand (residues 66-76) of beta-LG. Circular dichroic spectral analysis shows that carboxymethylation on beta-LG not only resulted in a substantial loss of beta-configuration but also exerted a 10 times increase in immunoreactivity as compared with heated beta-LG. The result suggests that a further disordered structure occurred in beta-LG and thus rendered the mAb recognition. Mutations on each charged residue (three Lys and one Glu) revealed that Lys-69 and Glu-74 were extremely essential in maintaining the antigenic structure. We also show an inverse relationship between the immunoreactivity in heated beta-LG and its binding to retinol or palmitic acid. Most interestingly, pH 9-10, which neutralizes the Lys groups of beta-LG, not only reduced its immunoreactivity but also its binding to palmitic acid implicating a role of Lys-69. Taken together, we concluded that strand D of beta-LG participated in the thermal denaturation between 70 and 80 degreesC and the binding to retinol and palmitic acid. The antigenic and biochemical roles of mAb specific to D strand are discussed in detail.
URI: http://dx.doi.org/10.1074/jbc.M407031200
http://hdl.handle.net/11536/14010
ISSN: 0021-9258
DOI: 10.1074/jbc.M407031200
期刊: JOURNAL OF BIOLOGICAL CHEMISTRY
Volume: 280
Issue: 5
起始頁: 3574
結束頁: 3582
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