The major XXXX -phosphorylated protein in the postsynaptic density fraction is @entity1024 receptor subunit 2B.

@entity1024 @entity2227 @entity10393 @entity50926 @entity143 @entity35 @entity669
The postsynaptic density (PSD) is a specialization of the submembranous cytoskeleton that is visible in the electron microscope on the cytoplasmic face of the postsynaptic membrane. A subcellular fraction enriched in structures with the morphology of PSDs contains signal-transduction molecules thought to regulate receptor localization and function in the central nervous system. We have purified a prominent @entity669 -phosphorylated glycoprotein of apparent molecular mass 180 kDa, termed PSD-gp180, that is highly enriched in the @entity35 forebrain PSD fraction. The sequences of four tryptic peptides generated from the protein reveal that it is the 2B subunit of the @entity1024 ( @entity143 ) type @entity2227 receptor. We have confirmed the identity of PSD-gp180 by showing that it reacts with antibodies raised against a unique fragment of the 2B subunit of the @entity143 receptor. We also show that the 2B subunit is the most prominently @entity669 -phosphorylated protein in the PSD fraction based upon recognition by an anti- @entity10393 antibody. Two types of @entity143 receptor subunits have been identified by molecular cloning [Nakanishi, S. (1992) Science 258, 597-603]. The single type 1 subunit is expressed throughout the brain and is necessary for formation of the receptor channel. The four type 2 subunits (2A, 2B, 2C, and 2D) are expressed in discrete brain regions, contain unusually long unique C termini, and confer distinct kinetic properties on @entity143 receptors that contain them. Our findings suggest that, in the forebrain, @entity143 receptor subunit 2B may serve to anchor @entity143 receptors at the postsynaptic membrane through its interaction with the PSD. The prominent presence of @entity50926 further suggests that the @entity143 receptor may be regulated by @entity669 phosphorylation or that it may participate in signaling through @entity669 phosphorylation and through its ion channel.
