title: Human ABR encodes a protein with GAPrac activity and homology to the DBL nucleotide exchange factor domain.
abstract: We have previously cloned a segment of a gene, ABR, homologous to the BCR gene, which encodes a protein consisting of three distinct functional domains. In the present study, genomic ABR sequences were used to isolate human ABR cDNAs. Surprisingly, the two types of ABR cDNAs identified differed only in their most 5' coding sequences. These are predicted to encode proteins of 93.5 and 92.3 kDa molecular mass. ABR showed a differential expression pattern in various mouse tissues, analogous to that of BCR, and the highest level was found in brain. Similar to BCR, ABR contains a region with homology to DBL, vav, and CDC24, which are likely to or have been shown to encode GTP exchange factors. A domain of ABR with similarity to GAPrho was expressed as a fusion protein in Escherichia coli and was shown to have GAP activity toward rac. Although both ABR and BCR have GAP activity, ABR lacks homology to the serine/threonine kinase domain of BCR. Therefore, ABR is likely to have cellular functions overlapping with but also distinct from those of BCR.
authors.affiliation: Department of Pathology, Childrens Hospital of Los Angeles, California 90027.
authors.forename: N
authors.initials: N
authors.lastname: Heisterkamp
authors.forename: V
authors.initials: V
authors.lastname: Kaartinen
authors.forename: S
authors.initials: S
authors.lastname: van Soest
authors.forename: G M
authors.initials: GM
authors.lastname: Bokoch
authors.forename: J
authors.initials: J
authors.lastname: Groffen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004247:DNA; D019204:GTP-Binding Proteins / Q000378:metabolism; D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D015513:Oncogene Proteins / Q000235:genetics; D011505:Protein-Tyrosine Kinases; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D051562:Proto-Oncogene Proteins c-bcr; D015682:Retroviridae Proteins, Oncogenic / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D020744:rac GTP-Binding Proteins
chemical_list: C082659:ABR protein, human; C484145:Abr protein, mouse; D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; C057811:MCF2 protein, human; C512843:Mcf2 protein, mouse; D015513:Oncogene Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D015682:Retroviridae Proteins, Oncogenic; D004247:DNA; D011505:Protein-Tyrosine Kinases; C496613:BCR protein, human; C496614:Bcr protein, mouse; D051562:Proto-Oncogene Proteins c-bcr; D019204:GTP-Binding Proteins; D020744:rac GTP-Binding Proteins