Studies on the Cell-Free Biosynthesis of CNS Membrane Proteins |
| |
Authors: | Jeffrey M Gilbert Paola Strocchi |
| |
Institution: | Neurochemistry Laboratory of the Laboratories for Psychiatric Research, Mailman Research Center, McLean Hospital, Belmont, and Department of Psychiatry, Harvard Medical School, Boston, Massachusetts, U.S.A. |
| |
Abstract: | Abstract: The biosynthesis of CNS membrane proteins was studied in cell-free systems containing membrane-bound polysomes (rough endoplasmic reticulum; RER) or free polysomes from rat forebrain. In previous studies of CNS membrane proteins using two-dimensional gel electrophoretic analysis, five proteins (mol. wt.-pI: 75K 5.4, 68K 5.6, 61K 5.1, 58K 5.1, and 36K 5.6) were found in ceil membrane fractions including preparations enriched in RER, smooth endoplasmic reticulum, and plasma membranes. One of these proteins, 68K 5.6, was also present in cytosol and comigrated with a microtubule-associated protein. In our present study, cell-free systems containing RER were found to synthesize the 75K 5.4, 61K 5.1, and 58K 5.1 proteins. A protein, 34K 5.65, similar (but not identical) to the 36K 5.6 protein was also synthesized. After cell-free synthesis, the 75K 5.4 and 58K 5.1 proteins could be purified by concanavalin A affinity chromatography. Of the five common membrane proteins previously identified, only the 68K 5.6 protein was synthesized by the free polysome population. The free polysomes were also found to synthesize cyclic AMP binding proteins at 48K and 54K, known from previous studies to be present in both cytosol and plasma membrane fractions in mammalian brain tissue. In conclusion, RER synthesized proteins found exclusively in CNS membrane fractions, whereas free polysomes synthesized those proteins found in both soluble and membrane compartments. |
| |
Keywords: | Brain protein synthesis Membrane proteins Microtubule-associated proteins Glycoproteins Rough endoplasmic reticulum Cyclic AMP binding proteins Tubulin |
|
|