Purification and molecular shape of a 144 kDa protein bearing N-acetylglucosamine residues from rat liver nuclear envelopes.

A 144 kDa protein was purified from the WGA-Sepharose bound fraction of a rat liver nuclear envelope salt-extract by hydroxyapatite HPLC (HAP HPLC). Two other, 120 and 86 kDa, proteins were also partially purified from the fraction by a combination of DEAE- and HAP-HPLCs. It was suggested that the 144, 120, and 86 kDa proteins bear GlcNAc residues, and are nucleoporins, because they were purified from nuclear envelopes, reacted with WGA-HRP, and cross-reacted with an antibody against p62 nucleoporin complexes. The sedimentation coefficients and Stokes' radii of these GlcNAc-bearing proteins were determined by glycerol density gradient centrifugation and gel filtration in the presence of 500 mM NaCl. The molecular masses calculated from these values suggested that these three proteins each exist as a monomer under the conditions employed. The axial ratios of the purified 144, 120, and 86 kDa GlcNAc-proteins were estimated to be 35, 31, and 31, respectively. These values suggested that they are rod-shaped molecules. The axial ratio of a purified nucleoporin-complex consisting of 62, 60, and 54 kDa components bearing GlcNAc was shown to be 20. This nucleoporin complex seems to be a rod-shaped complex. From these results, a rod shape is proposed to be a common characteristic of GlcNAc-proteins in nuclear envelopes.