Sad-1 And Unc-84 Domain Containing Protein 2 (SUN2)

SUN2 protein contains an N-terminal signal sequence, followed by 2 coiled-coil domains, 2 transmembrane domains, and a C-terminal SUN domain. Immunofluorescence microscopy demonstrated nuclear rim-like expression of epitope-tagged or endogenous SUN2 in HeLa cells. This localization was dependent on amino acids 26 to 339 of SUN2. Immunoblot and biochemical analyses showed expression of an 85-kD SUN2 protein. Further analyses revealed that SUN2 is a type II transmembrane protein with the SUN domain protruding in the periplasmic space between the INM and the ONM. The predicted proteins contain 824 and 724 amino acids, respectively, and their C termini share homology with the C termini of C. elegans Unc84 and S. pombe Sad1. Both SUN1 and SUN2 contain a transmembrane region.