Nup107 is a novel nuclear pore complex protein that contains a leucine zipper

We have previously described procedures for the isolation of potential nuclear pore complex proteins (nucleoporins or Nups) from rat liver nuclear envelopes and their subsequent subfractionation into those binding to wheat germ agglutinin (WGA) and those that do not. One of these non-WGA-reactive proteins, termed Nup155, was previously molecularly cloned and sequenced and by immunoelectron microscopy shown to be a bona fide nucleoporin. Here we have characterized a second protein of the non-WGA-reactive type and show that it is a Nup as well. Molecular cloning and sequencing revealed that the protein has a calculated molecular mass of 107.2 kDa. It is, therefore, termed Nup107 (for nucleoporin of 107 kDa). Like other Nups that have so far been analyzed, Nup107 contains an abundance of kinase consensus sites. However, the primary structure of Nup107 is unique and not similar to other proteins in the data banks. Its most striking feature is a leucine zipper in its carboxyl-terminal region.