The effect of C-terminal deletion on the folding and self-association of recombinant non-phosphorylated human beta-casein.
Recombinant human beta-casein (CN) mutants were prepared having 11, 22 and 31 amino acids (aa) deleted from the C-terminus. The temperature-dependent self-association of these and the wild-type recombinant was studied by turbidity (OD400) while possible folding differences were examined by intrinsic and extrinsic fluorescence intensity and fluorescence resonance energy transfer. There were major self-association and some conformational differences. Hydrophobicity profile and hydrophobic cluster analysis for bovine and human beta-CN suggested that the ability of the 31 aa deletion mutant in human beta-CN to self-associate when a comparable bovine deletion peptide would not may be due to the presence of additional hydrophobic regions in the middle, indicating that the human protein may contain more than a single hydrophobic binding locus and suggesting that the process for the formation and structure of the micelles of human milk may be quite different from that for bovine milk. A new model may be needed.
Bu
Hongyin
H
Department of Biochemistry and Microbiology, Biochemistry Division, School of Medicine, Loma Linda University, Loma Linda, CA 92350, USA.
Sood
Satish M
SM
Slattery
Charles W
CW
D000595:Amino Acid Sequence; D002364:Caseins / Q000737:chemistry* / Q000648:ultrastructure; D005260:Female; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D008895:Milk, Human / Q000737:chemistry; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D013696:Temperature
D002364:Caseins; D011994:Recombinant Proteins