Conformational dynamics underlie the activity of the auxin-binding protein, Nt-abp1.
The auxin-binding protein 1 (ABP1) has been proposed to be involved in the perception of the phytohormone at the plasma membrane. Site-directed mutagenesis was performed on highly conserved residues at the C terminus of ABP1 to investigate their relative importance in protein folding and activation of a functional response at the plasma membrane. Detailed analysis of the dynamic interaction of the wild-type ABP1 and mutated proteins with three distinct monoclonal antibodies recognizing conformation-dependent epitopes was performed by surface plasmon resonance. The influence of auxin on these interactions was also investigated. The Cys(177) as well as Asp(175) and Glu(176) were identified as critical residues for ABP1 folding and action at the plasma membrane. On the contrary, the C-terminal KDEL sequence was demonstrated not to be essential for auxin binding, interaction with the plasma membrane, or activation of the transduction cascade although it does appear to be involved in the stability of ABP1. Taken together, the results confirmed that ABP1 conformational change is the critical step for initiating the signal from the plasma membrane.
David
K
K
Institut des Sciences du Végétal, CNRS, 91198 Gif sur Yvette, Cedex, the Laboratoire d'Electrophysiologie des Membranes, Université de Paris 7, 75000 Paris, France.
Carnero-Diaz
E
E
Leblanc
N
N
Monestiez
M
M
Grosclaude
J
J
Perrot-Rechenmann
C
C
D000595:Amino Acid Sequence; D007210:Indoleacetic Acids / Q000378:metabolism / Q000494:pharmacology; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010940:Plant Proteins; D011487:Protein Conformation; D011956:Receptors, Cell Surface / Q000737:chemistry* / Q000502:physiology; D013329:Structure-Activity Relationship
D007210:Indoleacetic Acids; D010940:Plant Proteins; D011956:Receptors, Cell Surface; C083846:auxin-binding protein 1