PROTEIN HALF-LIVES OF 2 SUBUNITS OF AN NMDA RECEPTOR-LIKE COMPLEX, THE 71-KDA GLUTAMATE-BINDING AND THE 80-KDA CPP-BINDING PROTEIN

We determined the half-lives for two subunits of a complex that functi ons as a glutamate and N-methyl-D-aspartate (NMDA) receptor-ion channe l in synaptic membranes. These two proteins are a 71 kDa glutamate-bin ding protein (GBP) and an 80 kDa CPP-binding protein (CBP). Seven mont h-old Fischer 344 rats were injected with L-[C-14] leucine. The radioa ctivity in the two proteins was determined in a crude synaptosomal mem brane fraction obtained from the brains of rats sacrificed from 4 hour s to 13 days after the injection. The previously reported data on time -dependent appearance and loss of L-[C-14] leucine radioactivity in th e serum (Ferrington et al., 1997, Biochem. Biophys. Res. Commun. 237, 163-165) was used in the present study to estimate the half-lives of G BP and CBP. Theoretical curves best fit the experimental data obtained for the two proteins assuming apparent half-lives of 14 (+/-2.4) and 18 (+/-1.2) hours for CBP and GBP, respectively. (C) 1997 Academic Pre ss.