Purification of a novel apolipoprotein H-like milk protein with ribonucleolytic and cell-free translation inhibitory activities.
A new whey protein designated apolipoprotein H-like whey protein, with a molecular weight of 62 kDa and an N-terminal amino acid sequence similar to that of apolipoprotein H, was isolated from bovine milk. The isolation procedure involved removal of globulin from acid whey by precipitation with 1.8M (NH4)2SO4, followed by addition of (NH4)2SO4 to attain a concentration of 3.6M. Subsequent steps included chromatography on CM-Sepharose and Mono S and elution of the adsorbed protein of interest with a linear NaCl gradient. The new whey protein displayed some ribonuclease (RNase) activity. It was most active at pH 7.5 with yeast transfer RNA (tRNA) as substrate and showed potent specific ribonucleolytic activity toward poly C. It inhibited cell-free translation in a rabbit reticulocyte lysate system with an IC50 of approximately 63 nM.
Ye
X Y
XY
Department of Biochemistry, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, NT, People's Republic of China.
Ng
T B
TB
D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D002474:Cell-Free System; D006023:Glycoproteins / Q000302:isolation & purification*; D008894:Milk Proteins / Q000302:isolation & purification*; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis / Q000187:drug effects*; D011817:Rabbits; D012260:Ribonucleases / Q000302:isolation & purification*; D053482:beta 2-Glycoprotein I
D006023:Glycoproteins; D008894:Milk Proteins; D053482:beta 2-Glycoprotein I; D012260:Ribonucleases