It has also been demonstrated that Pma1 molecules are relatively mobile within these patches. The study of lateral mobility and oligomerization of transmembrane proteins has been based mainly on the phenomenon of fluorescence resonance energy transfer. When the donor and the acceptor carry different fluorophores, the distance between them can be assessed by changes in the fluorescence Salvianolic-acid-C emission spectrum. If the donor and acceptor molecules carry the same fluorophore, then the intermolecular interactions can be studied by the change in fluorescence anisotropy. The latter method has been denoted as homo-FRET and has been widely used recently to estimate the degree of protein oligomerization. Thus, it is clear that glucose activation of Pma1 is a complex process including several levels. In this work, we have attempted to assess the role of sphingolipid and ergosterol in the glucose activation of Pma1 and the mobility of yeast Pma1 molecules under glucose-induced activation of the enzyme. Appropriate blanks were measured using GFP-lacking cells. The difference between the cell concentrations of the main and the reference solutions was estimated from their absorbance at 600 nm. Each contribution of the reference Anacetrapib solution was corrected for this difference using the Beer-Lambert law. The blanks were subtracted from each of the fluorescence intensity values and used to calculate the anisotropy values. All of the fluorescence anisotropy values were corrected for the instrumental G factor, which was measured using a highly diluted aqueous solution of fluorescein. Thus, we have shown that sphingolipid but not ergosterol is important for glucose activation of Pma1. This fact can be explained as follows: One of the consequences of sphingolipid synthesis disturbance in the lcb1-100 strain is inefficient or completely blocked Pma1 oligomerization, which probably results in the elimination of glucose activation. The difference in glucose effects on Pma1 activity in the erg6 and lcb1100 strains may, therefore, be attributed to the sphingolipid associating with the protein at the very initial stages of biosynthesis of the enzyme and determining its oligomeric structure. Ergosterol, the other component of the lipid raft, appears not to participate directly in the formation of the oligomeric Pma1 complex and have no particular effect on the functioning of the protein. The idea that oligomerization of Pma1 is necessary for the glucose activation of Pma1 was indirectly confirmed in the earlier work. Using electron crystallography, researchers showed that the cytoplasmic part of Pma1 in a ligand-free form consists of four domains. Domain two of one Pma1 molecule directly contacts domain three of the neighboring molecule. Unfortunately, the authors of this work did not link these structural domains with the functional domains. However, it may be hypothesized that in the absence of glucose, the nucleotide-binding domain of the Pma1 molecule is locked by the C-domain of the neighboring Pma1 molecule. In this case, glucose activation of the enzyme results in successive phosphorylation of Ser-911 and Thr-912, followed by the release of the Ctail from the nucleotide-binding domain, as demonstrated previously. Taking into account the intermolecular character of the described event, it may be supposed that Pma1 oligomerization is necessary for the activation of Pma1 by glucose. Since the modern concept of glucose activation of Pma1 presupposes the movement of its C-tail, this process could be traced using the strain PMA1-GFP, the Pma1 molecule of which carries a GFP domain at the C-terminus.