Membrane glycoproteins and plant and animal proteins with lectin or lectin-like properties.

Abstract

The fat cell, chiefly from porcine greater omentum, was treated with hypertonic sodium chloride and membranes left over from exuded fat were extracted with Triton X-100 and the extract subjected to gel electrophoresis. Of the 20 or more bands which showed on the gel, at least five were periodate-Schiff positive. By the treatment of the glycoproteins with Con A, followed by DEAE-cellulose, one with an apparent molecular weight of 74 kDA was obtained pure. The other components are not yet purified. However, two glycoproteins of apparent molecular weights of 89 and 112 kDa were obtained from the fat cell membrane by affinity chromatography. These were apparently lectins, since they possessed hemagglutinating activity and specificity towards maltose and caused adhesion among cells (erythrocytes) and aggregation of fat cells. The properties of lectins from various sources have also been studied: rice germ lectin, Allium sativum lectin, a lectin from a species of silkworm and one from loquat leaves. A crystalline protein called pinellin was isolated from Pinella ternata. Since it has been shown to exhibit cell aggregation and mitogenic activity, it is also a lectin, showing species as well as cell type specificity. Preliminary studies have also been made of the binding of pinellin to its receptor on fat cells. The protein has also been shown to possess an anti-implantation effect in rabbits. Studies have been made of membrane proteins on ram spermatozoa and Con A receptors on squamous epithelial cancer cells.