Bouguyon Edwige, Beauvallet Christian, Huet Jean-Claude, Chanat Eric
Institut National de la Recherche Agronomique, Laboratoire de Génomique et Physiologie de la Lactation, Jouy-en-Josas, F-78352, France.
Biochem Biophys Res Commun. 2006 May 5;343(2):450-8. doi: 10.1016/j.bbrc.2006.03.005. Epub 2006 Mar 10.
Mammary epithelial cells synthesised and secreted caseins, the major milk proteins in most mammals, as large aggregates called micelles into the alveolar lumen they surround. We investigated the implication of the highly conserved cysteine(s) of kappa-casein in disulphide bond formation in casein micelles from several species. Dimers were found in all milks studied, confirming previous observation in ruminants. More importantly, the study of interchain disulphide bridges in mouse and rat casein micelles revealed that any casein possessing a cysteine is engaged in disulphide bond interchange; these species express four or five cysteine-containing caseins, respectively. We found that the main rodent caseins form both homo- and heterodimers. Additionally, disulphide bond formation among milk proteins was specific since the interaction of the caseins with cysteine-containing whey proteins was not observed in native casein micelles.
乳腺上皮细胞合成并分泌酪蛋白，酪蛋白是大多数哺乳动物乳汁中的主要蛋白质，以称为微胶粒的大聚集体形式分泌到它们所包围的肺泡腔中。我们研究了κ-酪蛋白中高度保守的半胱氨酸在几种物种的酪蛋白微胶粒中二硫键形成中的作用。在所有研究的乳汁中都发现了二聚体，证实了之前在反刍动物中的观察结果。更重要的是，对小鼠和大鼠酪蛋白微胶粒中链间二硫键的研究表明，任何含有半胱氨酸的酪蛋白都参与二硫键交换；这些物种分别表达四种或五种含半胱氨酸的酪蛋白。我们发现主要的啮齿动物酪蛋白形成同二聚体和异二聚体。此外，乳蛋白之间的二硫键形成具有特异性，因为在天然酪蛋白微胶粒中未观察到酪蛋白与含半胱氨酸的乳清蛋白之间的相互作用。
