Ninein is one of the proteins important for centrosomal function. This protein is important for positioning and anchoring the microtubules minus-ends in epithelial cells. Localization of this protein to the centrosome requires three leucine zippers in the central coiled-coil domain. Multiple alternatively spliced transcript variants that encode different isoforms have been reported. The deduced 2047aa protein has a calculated molecular mass of 239kD. NIN contains an N-terminal GTP-binding site, a large coiled-coil domain with 4 leucine zipper motifs, and a C-terminal domain responsible for GSK binding. Unlike mouse Nin, it does not have an N-terminal Ca(2+)-binding site. Northern blot analysis detected a 9.0-kb transcript in all tissues examined and a 7.0-kb transcript predominantly in heart and skeletal muscle.