The study of most membrane proteins remains challenging due to their hydrophobicity and their low natural abundance in cells. Lactococcus lactis, a Gram-positive lactic bacterium, has been traditionally used in food fermentations and is nowadays widely used in biotechnology for large-scale production of heterologous proteins. This system has been successfully used for the production of prokaryotic and eukaryotic membrane proteins. The purpose of this chapter is to provide detailed protocols for (1) the expression of plant peripheral or intrinsic membrane proteins and then for (2) their solubilization, from Lactococcus membranes, for further purification steps and biochemical characterization.