The lamin B receptor‐associated protein p34 shares sequence homology and antigenic determinants with the splicing factor 2‐associated protein p32

Abstract

The lamin B receptor (p58) is an inner nuclear membrane protein that forms an in vivo complex with the nuclear lamins, a nuclear envelope kinase, and two other nuclear proteins with apparentM _r of 18,000 (p18) and 34,000 (p34). We now report the isolation of p34 by partial dissociation of the immunoaffinity‐purified p58 protein complex. Determination of the N‐terminal amino acid sequence of purified p34 shows that this polypeptide is homologous to p32, a splicing factor 2 (SF2)‐associated protein. The relatedness between p34 and p32 can be further established by showing that antibodies raised against N‐ and C‐terminal peptides of p32 cross‐react with purified p34. As the amino acid sequence of p58 contains an arginine/serine (RS)‐rich region similar to the RS‐rich region found in SF 2, we speculate that these domains provide binding sites for p34 and that this protein may be a linker between the nuclear membrane and intranuclear spliceosomal substructures.