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: | 4-二月-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 |
顯示於類別: | 期刊論文 |