Developmental changes in protein carboxylmethylation and in the benzodiazepine receptor proteins in rat brain

The intraventricular administration of [ 3H-methyl]-methionine resulted in a steady increase in carboxyl-[ 3H]methylated protein formation in the brain of developing rats (2–42 days). The analysis by gel filtration on Sepharose-4B of Lubrol-P x-solubilized membrane proteins, including benzodiazepine receptor proteins, revealed co-migration of carboxyl-[ 3H]methylated and [ 3H]flunitrazepam-binding protein species. The latter displayed a single peak at 2 days and 2–3 peaks subsequently. At 26 days the lighter of the two [ 3H]flunitrazepam and [ 3H]muscimol-binding peaks associated with the principal carboxyl-[ 3H]methylated protein peak. The findings suggest the participation of carboxylmethylation in the maturation of benzodiazepine receptor proteins.