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 o f a rat liver nuclear envelope salt-extract by hydroxyapatite HPLC (HA P HPLC). Two other, 120 and 86 kDa, proteins were also partially purif ied 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 envelop es, reacted with WGA-HRP, and cross-reacted with an antibody against p 62 nucleoporin complexes. The sedimentation coefficients and Stokes' r adii of these GlcNAc-bearing proteins mere determined by glycerol dens ity gradient centrifugation and gel filtration in the presence of 500 mM NaCl. The molecular masses calculated from these values suggested t hat 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 val ues suggested that they are rod-shaped molecules. The axial ratio of a purified nucleoporin-complex consisting of 62, 60, and 54 kDa compone nts bearing GlcNAc was shown to be 20. This nucleoporin complex seems to be a rod-shaped complex. From these results, a rod shape is propose d to be a common characteristic of GlcNAc-proteins in nuclear envelope s.