Chemical synthesis and structure elucidation of bovine κ-casein (1–44)

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• 作者：Paramjit S. Bansal ; Paul A. Grieve ; Ronald J. Marschke ; Norelle L. Daly ; Emily McGhie ; David J. Craik and Paul F. Alewood
• 关键词：Solid-phase peptide synthesis ; 2D NMR ; Milk protein ; κ ; -Casein ; Helical structure
• 刊名：Biochemical and Biophysical Research Communications
• 出版年：2006
• 出版时间：24 February 2006
• 年：2006
• 卷：340
• 期：4
• 页码：1098-1103
• 全文大小：366 K

文摘

The caseins (α_s1, α_s2, β, and κ) are phosphoproteins present in bovine milk that have been studied for over a century and whose structures remain obscure. Here we describe the chemical synthesis and structure elucidation of the N-terminal segment (1–44) of bovine κ-casein, the protein which maintains the micellar structure of the caseins. κ-Casein (1–44) was synthesised by highly optimised Boc solid-phase peptide chemistry and characterised by mass spectrometry. Structure elucidation was carried out by circular dichroism and nuclear magnetic resonance spectroscopy. CD analysis demonstrated that the segment was ill defined in aqueous medium but in 30 % trifluoroethanol it exhibited considerable helical structure. Further, NMR analysis showed the presence of a helical segment containing 26 residues which extends from Pro⁸ to Arg³⁴. This is the first report which demonstrates extensive secondary structure within the casein class of proteins.