Kim H H, Jimenez-Flores R
Department of Food Science, University of Illinois, Urbana 61801, USA.
J Dairy Sci. 1995 Jan;78(1):24-35. doi: 10.3168/jds.S0022-0302(95)76612-7.
Milk fat globule membrane proteins in washed cream were analyzed using preparative isoelectric focusing followed by SDS-PAGE. Five major protein bands of milk fat globule membrane were observed with apparent molecular mass of 150, 67, 62.5, 51, and 49 kDa. The protein of band 5 (49 kDa) was well separated from the protein of band 4 (51 kDa). Heat-induced effects (72 and 87 degrees C for 2.5, 5, 10, 20, 30, and 60 min) on whole milk proteins were also investigated under nonreducing and reducing conditions to study disulfide interactions between serum proteins and those in the fat membrane. beta-Lactoglobulin and other milk serum proteins interacted readily with milk fat globule membrane and membrane proteins at 87 degrees C, but only slightly at 72 degrees C. However, the interactions between serum proteins and fat globule membrane proteins cannot be explained solely by disulfide linkage formation. Some membrane proteins, especially the 49-kDa protein (band 5), underwent drastic changes after heat treatment. Further characterization of the 49-kDa protein demonstrated that it binds concanavalin A; AA composition and N-terminal sequence of the protein were determined and compared with those reported in the literature.
采用制备性等电聚焦随后进行SDS-PAGE分析了洗涤稀奶油中的乳脂肪球膜蛋白。观察到乳脂肪球膜的五条主要蛋白带，其表观分子量分别为150、67、62.5、51和49 kDa。第5条带（49 kDa）的蛋白与第4条带（51 kDa）的蛋白分离良好。还在非还原和还原条件下研究了热诱导效应（72和87℃，处理2.5、5、10、20、30和60分钟）对全脂乳蛋白的影响，以研究血清蛋白与脂肪膜蛋白之间的二硫键相互作用。β-乳球蛋白和其他乳清蛋白在87℃时很容易与乳脂肪球膜和膜蛋白相互作用，但在72℃时只有轻微相互作用。然而，血清蛋白与脂肪球膜蛋白之间的相互作用不能仅用二硫键形成来解释。一些膜蛋白，尤其是49 kDa的蛋白（第5条带），在热处理后发生了剧烈变化。对49 kDa蛋白的进一步表征表明它能结合伴刀豆球蛋白A；测定了该蛋白的氨基酸组成和N端序列，并与文献报道的进行了比较。
