RanBP-Type And C3HC4-Type Zinc Finger Containing Protein 1 (RBCK1)

RBCK1 is similar to mouse UIP28/UbcM4 interacting protein. The deduced 468-amino acid protein contains a C3HC4 zinc finger and 3 protein kinase C (PKC) substrate recognition sites. Northern blot analysis detected a XAP3 transcript of 2.5 to 3.0 kb. Expression was high in brain, placenta, and pancreas, intermediate in heart and skeletal muscle, and low in lung, liver, and kidney.The 260-amino acid variant Rbck2 is identical to Rbck1 up to the 2 central coiled-coil domains, but it has 20 unique C-terminal residues. Both proteins also contain a classic leucine-rich nuclear export signal, but only Rbck1 contains a C-terminal nuclear localization signal. Rbck2 was expressed in the cytoplasm of transfected HEK293 cells, and Rbck1 appeared to shuttle between the cytoplasm and nucleus.