Characterization
of Nep2,
a polytopic nuclear membrane protein.
Arunas Leipus (1),
Jean-Marc Berrez (2), Ann Mutvei-Berrez (2)
(1) Department of Biochemistry, Umeå University, University Campus, Umeå,
S-90187, Sweden (Arunas.Leipus@chem.umu.se); (2) Department of Natural
Sciences, Södertörns University College, S-141 89 Huddinge, Sweden
The nuclear envelope is intimately involved in the organisation and function of the different sub-compartments of the nucleus. Even though the nuclear envelope contains a large number of membrane proteins, very few have been identified. We have characterized a conserved nuclear membrane protein from yeast to human. Nep2 consists of 16 trans membrane regions and a long negatively charged hydrophilic C-terminus. The overall structure of the protein resembles a channel while the soluble C-terminal part folds like a DNA-binding protein. Peptide antibodies against the C-terminus region have been used to localize Nep2 in the cell. It is found at the inner membrane of the nuclear envelope as a ring around the nucleus and does not co-localize with the pore complex. An additional staining was observed in the nucleolus. The knock out mutant of Nep2 has a ts phenotype at 39 degrees C, which is rescued by adding divalent cations such as Mg2+ and Ca2+. Screening for interacting components by high copy suppression at 39 degrees C resulted in two genes. The genes are coding for a serine threonine phosphatase and a protein involved in nucleolar functions. The study of the interactions with these suppressors will shed some light on the function of Nep2.