Modelling of auxin-binding protein 1 suggests that its C-terminus and auxin could compete for a binding site that incorporates a metal ion and tryptophan residue 44.
Sequence comparison indicates that auxin-binding protein 1 (ABP1) belongs to a family of proteins with the core beta-barrel structure of the vicilins. Previous modelling within this family correctly predicted metal-ion binding and oligomeric properties of oxalate oxidase. ABP1 also contains a putative metal-ion-binding cluster of amino acids, adjacent to a tryptophan side chain, leading to a proposed auxin-binding site that incorporates metal-ion interaction with the auxin carboxylate. Modelling implicates W44 (Zea mays ABP1) in auxin binding, rather than W136 or W151. Reduced sequence similarity for the C-terminal region prevents model building. It is proposed that one of these C-terminal tryptophans, along with a neighbouring negatively charged side chain, occupies the binding pocket in the absence of auxin, thereby linking auxin binding to conformational change and C-terminal involvement in signalling.
Warwicker
J
J
Institute of Biomedical and Life Sciences, Glasgow University, UK. jim.warwicker@umist.ac.uk
D000429:Alcohol Oxidoreductases; D000595:Amino Acid Sequence / Q000502:physiology; D001665:Binding Sites / Q000502:physiology; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D007210:Indoleacetic Acids / Q000737:chemistry / Q000378:metabolism*; D019476:Insect Proteins; D008670:Metals / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism; D010940:Plant Proteins; D011487:Protein Conformation; D014364:Tryptophan / Q000378:metabolism; D003313:Zea mays / Q000737:chemistry
D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D007210:Indoleacetic Acids; D019476:Insect Proteins; D008670:Metals; D010750:Phosphoproteins; D010940:Plant Proteins; C092382:arylphorin-binding proteins, insect; D014364:Tryptophan; D000429:Alcohol Oxidoreductases; C096794:C-terminal binding protein