Differentially Expressed In FDCP 6 (DEF6)

DEF6 contains 631 amino acids and has a calculated molecular mass of 74 kD. It shares 92% amino acid identity with its mouse homolog and 45% identity with SWAP70. IBP has an N-terminal EF-hand motif, a central pleckstrin homology (PH) domain containing a potential bipartite basic nuclear localization signal, and a C-terminal alpha-helical DBL homology (DH) region. Western blot analysis showed an approximately 75-kD protein in T and B cells, but not fibroblasts. Northern blot analysis revealed abundant expression of a 2.4-kb transcript in all lymphoid tissues examined except fetal liver. Immunofluorescence microscopy demonstrated expression in tonsillar T cells and in coronal B cells, but not in germinal center B cells or macrophages.