Chemical synthesis and structure elucidation of bovine kappa-casein (1-44).
The caseins (alphas1, alphas2, beta, and kappa) 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 kappa-casein, the protein which maintains the micellar structure of the caseins. kappa-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.
Bansal
Paramjit S
PS
Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Qld 4072, Australia.
Grieve
Paul A
PA
Marschke
Ronald J
RJ
Daly
Norelle L
NL
McGhie
Emily
E
Craik
David J
DJ
Alewood
Paul F
PF
D000595:Amino Acid Sequence; D000818:Animals; D002364:Caseins / Q000138:chemical synthesis / Q000737:chemistry* / Q000648:ultrastructure*; D002417:Cattle; D003198:Computer Simulation; D003461:Crystallography; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017433:Protein Structure, Secondary
D002364:Caseins