This family consists of several eukaryotic SH3 domain-binding protein 5 or c-Jun N-terminal kinase (JNK)-interacting proteins (SH3BP5 or Sab). Sab binds to and serves as a substrate for JNK in vitro, and has been found to interact with the Src homology 3 (SH3) domain of Bruton's tyrosine kinase (Btk). Inspection of the sequence of Sab reveals the presence of two putative mitogen-activated protein kinase interaction motifs (KIMs) similar to that found in the JNK docking domain of the c-Jun transcription factor, and four potential serine-proline JNK phosphorylation sites in the C-terminal half of the molecule [].This entry also includes REI-1 and REI-2 from C. elegans. REI-1 is a guanine nucleotide exchange factors (GEFs) for RAB-11. It functions in early embryos [].
