Recombinant Mouse PLTP Protein

Phospholipid transfer protein (PLTP; also known as lipid transfer protein II) is an 80 kDa, secreted glycoprotein, that belongs to the BPI/LBP/Plunc superfamily of molecules (1). It is synthesized as a precursor with a 17 amino acid (aa) signal sequence and a 476 aa mature chain. The mature chain contains two BPI/LBP/CETP domains (aa 21 - 239 and 263 - 463) and seven potential sites for N-linked glycosylation. Mature mouse PLTP shares 83% aa sequence identity with mature human PLTP (3). PLTP is expressed by a wide variety of tissues and is secreted by macrophages. Northern blot analysis shows the order of PLTP mRNA expression as follows: lung > adipose tissue, placenta, testis > brain > muscle, heart, liver (2). PLTP is a multifunctional, extracellular lipid transfer protein that plays a major role in lipoprotein metabolism and atherosclerosis (4 - 6). In addition to phospholipids, PLTP transfers several amphipatic compounds, including unesterified cholesterol, lipopolysaccharides, diacylglycerides, and alpha-tocopherol, the main isomer of vitamin E (4). According to several studies, PLTP not only affects plasma lipid and lipoprotein profiles, but also modulates cell physiology (4, 7 - 11). In mice, systemic PLTP deficiency proves to be atheroprotective, whereas PLTP overexpression is proatherogenic (4, 6). However, macrophage PLTP is shown to be atheroprotective (4, 6).