Expression and characterization of a lysine rich protein in cow milk

Abstract

The lysine is considered as the most important essential amino acid, because it is the most limiting in the cereals grains. In this study, a lysine-rich (LR) gene and the expression vector pcDNA3.1-LR and pBC1-LR were constructed. The LR was expressed in 293T cells driven by the vector pcDNA3.1-LR and checked by RT-PCR and WB. The mammary gland tissue-specific expression vector carrying the LR was injected directly into the lactating mammary glands of cows and the milk samples were checked by a complete amino acid analysis. The results showed that the LR protein was expressed successfully in cells and in cow milk; the expression of LR lasted for 6 d, and the lysine level of the injection group was significantly higher than that of negative controls (p <0.05). This study provide a better understanding of how mammary gland expression systems increase the lysine content of milk that can be applied to transgenic dairy cow.