Competition between Delta and the Abruptex domain of Notch.
BACKGROUND
Extracellular domains of the Notch family of signalling receptors contain many EGF repeat domains, as do their major ligands. Some EGF repeats are modified by O-fucosylation, and most have no identified role in ligand binding.


RESULTS
Using a binding assay with purified proteins in vitro, it was determined that, in addition to binding to Delta, the ligand binding region of Notch bound to EGF repeats 22-27 of Notch, but not to other EGF repeat regions of Notch. EGF repeats 22-27 of Drosophila Notch overlap the genetically-defined 'Abruptex' region, and competed with Delta for binding to proteins containing the ligand-binding domain. Delta differed from the Abruptex domain in showing markedly enhanced binding at acid pH. Both Delta and the Abruptex region are heavily modified by protein O-fucosylation, but the split mutation of Drosophila Notch, which affects O-fucosylation of EGF repeat 14, did not affect binding of Notch to either Delta or the Abruptex region.


CONCLUSIONS
The Abruptex region may serve as a barrier to Notch activation by competing for the ligand-binding domain of Notch.
Pei
Zifei
Z
Department of Molecular Genetics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA. zpei@aecom.yu.edu
Baker
Nicholas E
NE
D000818:Animals; D004331:Drosophila melanogaster / Q000378:metabolism*; D005643:Fucose / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D047908:Intracellular Signaling Peptides and Proteins; D008024:Ligands; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011961:Receptors, Fc / Q000378:metabolism; D051880:Receptors, Notch / Q000737:chemistry* / Q000378:metabolism*; D020449:Repetitive Sequences, Amino Acid
D047908:Intracellular Signaling Peptides and Proteins; D008024:Ligands; D008565:Membrane Proteins; D050505:Mutant Proteins; D011961:Receptors, Fc; D051880:Receptors, Notch; C064045:delta protein; D005643:Fucose