Membranome

Abstract: The hammerhead ribozyme (HHR) is one of smallest catalytic RNAs, composed of a catalytic core and three stems; it undergoes self-cleavage in the presence of divalent magnesium ions (Mg(2+)) or other cations. It is hypothesized that the function and metabolism of RNAs might be regulated via interaction with lipid membranes in the prebiotic world. Using synthetic RNAs that model the core fragment of hammerhead ribozyme-like assembly (HHR-a), we investigated the enhancement of the self-cleavage reaction of HHR-a induced by the liposomes, both in the absence and presence of Mg(2+). The HHR-a activity was enhanced by 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE)/1,2-dioleoyl-sn-glycero-3-phosphocholine (DPPC) = 8/2 liposome with Mg(2+), while other liposomes did not so significant. In the presence of DOPE/DPPC = 8/2 liposome, the HHR-a activity was observed without Mg(2+), revealed by the conformational change of the HHR inhibitor complex induced by the interaction with the liposome. The UV resonance Raman spectroscopy analysis investigated the interaction between lipid molecules and nucleobases, suggesting that the ethanolamine group of DOPE molecules are assumed to act as monovalent cations alternative to Mg(2+), depending on the liposome membrane characteristics.

Abstract: Analyses of proteins from a number of proteomic studies of cell membranes have demonstrated that a significant component of the identified proteins is not predicted to contain transmembrane regions. The presence of such proteins may arise as a result of contamination of the membrane preparations or through real associations. Our aim was to identify integral proteins as well as those that are intimately associated with the microsomal membranes of K562 cells. Isolated membranes were treated under conditions reported to remove noncovalently associated ‘peripheral’ proteins and the residual proteins were SDS-PAGE-separated and analyzed by LC−MS/MS. Tandem lectin affinity was also examined as a complementary approach for the enrichment of membrane glycoproteins. Approximately 41% of the isolated proteins were assigned as membrane proteins based on the presence of transmembrane regions or covalent post-translational modifications that could account for membrane association. Collectively, these results indicate ...