Maclura pomifera agglutinin or lectin (MPA/MPL) is tetrameric plant protein purified by fractionation. MPA has a molecular weight of about 44,000 and consists of four subunits. It has an isoelectric point between pH 4.8 and pH 5.3, and blood group specificity towards A, B, and O (-SA). This lectin has a high affinity for tumor-associated T-antigen disaccharide (Galβ1,3GalNAcα) and many O-linked glycopeptide structures. The structure of Galβ1,3GalNAcα occurs on the surface of tumor cells as a mucin-associated antigenic marker, termed as T-antigen. It is also the central element in O-linked glycopeptide structures on other mammalian glycoproteins.
Texas Red is a red-fluorescent dye and when bound to Maclura pomifera Lectin (MPL/MPA) can show the binding pattern of this lectin in cellular imaging applications. There is very little overlap between the emission spectra of Texas Red and FITC making this combination ideal for dual-labeling experiments. Rhodamine dyes, such as Texas Red, are more photostable and less sensitive to pH change when compared to other dyes such as fluorescein.