XPA Binding Protein 1 (XAB1)

XAB1 specifically bound residues 30 to 34 of XPA. XAB1 expressed in insect cells had GTPase activity, but not ATPase activity. The deduced 374-amino acid protein has a calculated molecular mass of 41 kD. The N-terminal region contains several motifs conserved in GTP-binding proteins, and the C-terminal region contains a cluster of acidic amino acids. Northern blot analysis detected ubiquitous expression of a major 2.1-kb transcript, with highest expression in testis. A minor 2.9-kb transcript was detected in several tissues, and a minor 1.4-kb transcript was detected only in testis. Immunofluorescence analysis of HeLa cells and Western blot analysis of fractionated HeLa cells showed that XAB1 was predominantly cytoplasmic. Database analysis revealed XAB1 homologs in nematode, fly, and yeast.