A method was developed for isolation of native ribosomal subunits from rat gastrocnemius muscle. Native 40 S subunits which were isolated by this method retained their associated nonribosomal proteins and consisted primarily of particles with equilibrium densities of 1.41 and 1.48 g/cm3. Based on the binding of radiolabeled Met-tRNA(i)(Met), the 1.41 g/cm3 particle was identified as the 40 S initiation complex. Insulin deficiency in vivo resulting from either diabetes or fasting led to a 2-fold increase in 75 S monomers but had no effect on the numbers of native 40 and 60 S subunits or the relative distribution of the 1.41 and 1.48 g/cm3 particles. The rate of protein synthesis in perfused muscle preparations derived from insulin-deficient rats was reduced to about half the control value. Addition of insulin to the perfusate restored protein synthesis and 75 S monomers to control levels. The effect of insulin on protein synthesis was associated with a 1.5-fold increase in the amount of Met-tRNA(i)(Met) bound to the 1.41 g/cm3 particle. These findings identify formation of 40 S initiation complexes as a site of action of insulin on protein synthesis in skeletal muscle.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of Biological Chemistry|
|State||Published - 1985|
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Cell Biology