Abstract
In animals, heterotrimeric guanine nucleotide-binding protein (G protein) signaling is initiated by G protein-coupled receptors (GPCRs), which activate G protein α subunits; however, the plant Arabidopsis thaliana lacks canonical GPCRs, and its G protein α subunit (AtGPA1) is self-activating. To investigate how AtGPA1 becomes activated, we determined its crystal structure. AtGPA1 is structurally similar to animal G protein α subunits, but our crystallographic and biophysical studies revealed that it had distinct properties. Notably, the helical domain of AtGPA1 displayed pronounced intrinsic disorder and a tendency to disengage from the Ras domain of the protein. Domain substitution experiments showed that the helical domain of AtGPA1 was necessary for self-activation and sufficient to confer self-activation to an animal G protein α subunit. These findings reveal the structural basis for a mechanism for G protein activation in Arabidopsis that is distinct from the well-established mechanism found in animals.
Publication types
-
Research Support, N.I.H., Extramural
-
Research Support, Non-U.S. Gov't
MeSH terms
-
Adenosine Diphosphate / chemistry
-
Adenosine Diphosphate / metabolism
-
Adenosine Triphosphate / chemistry
-
Adenosine Triphosphate / metabolism
-
Amino Acid Sequence
-
Arabidopsis Proteins / chemistry*
-
Arabidopsis Proteins / genetics
-
Arabidopsis Proteins / metabolism
-
Circular Dichroism
-
Crystallization
-
GTP-Binding Protein alpha Subunits / chemistry*
-
GTP-Binding Protein alpha Subunits / genetics
-
GTP-Binding Protein alpha Subunits / metabolism
-
Guanine Nucleotide Exchange Factors / chemistry
-
Guanine Nucleotide Exchange Factors / metabolism
-
Kinetics
-
Models, Molecular
-
Molecular Sequence Data
-
Mutation
-
Protein Binding
-
Protein Folding
-
Protein Structure, Secondary*
-
Protein Structure, Tertiary
-
Receptors, G-Protein-Coupled / chemistry
-
Receptors, G-Protein-Coupled / metabolism
-
Sequence Homology, Amino Acid
-
Signal Transduction*
-
X-Ray Diffraction
Substances
-
Arabidopsis Proteins
-
GPA1 protein, Arabidopsis
-
GTP-Binding Protein alpha Subunits
-
Guanine Nucleotide Exchange Factors
-
Receptors, G-Protein-Coupled
-
Adenosine Diphosphate
-
Adenosine Triphosphate