Protein-lipid interactions in the sialic acid incorporating system of liver microsomes.
The conditions for the incorporation of sialic acid (N-acetylneuraminic acid) from CMP-sialic acid into endogenous acceptors of rat liver microsomes has been studied. It is shown that the incorporating activity can be solubilized by extraction of the microsomes with a mild detergent, Triton X-100. The specific activity of the soluble system is about sixfold compared to the original microsomes. Removal of lipids from the system greatly reduces its ability to incorporate sialic acid. Recombination with phospholipids prepared from liver microsomes restores the activity. Other lipids are ineffective, and single phospholipid fractions are less effective than the phospholipid mixture. It is concluded that the system studied, comprising both sialyl transferase and sialyl acceptor-protein is a typical intrinsic membrane protein system, dependent on a hydrophobic environment for full activity.
D000096:Acetone; D000818:Animals; D001665:Binding Sites; D003597:Cytosine Nucleotides / Q000378:metabolism; D007700:Kinetics; D050356:Lipid Metabolism; D008862:Microsomes, Liver / Q000378:metabolism*; D011092:Polyethylene Glycols; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D012794:Sialic Acids / Q000378:metabolism*
D003597:Cytosine Nucleotides; D011506:Proteins; D012794:Sialic Acids; D000096:Acetone; D011092:Polyethylene Glycols