Membrane association, mechanism of action, and structure of Arabidopsis embryonic factor 1 (FAC1).
Embryonic factor 1 (FAC1) is one of the earliest expressed plant genes and encodes an AMP deaminase (AMPD), which is also an identified herbicide target. This report identifies an N-terminal transmembrane domain in Arabidopsis FAC1, explores subcellular fractionation, and presents a 3.3-A globular catalytic domain x-ray crystal structure with a bound herbicide-based transition state inhibitor that provides the first glimpse of a complete AMPD active site. FAC1 contains an (alpha/beta)(8)-barrel characterized by loops in place of strands 5 and 6 that places it in a small subset of the amidohydrolase superfamily with imperfect folds. Unlike tetrameric animal orthologs, FAC1 is a dimer and each subunit contains an exposed Walker A motif that may be involved in the dramatic combined K(m) (25-80-fold lower) and V(max) (5-6-fold higher) activation by ATP. Normal mode analysis predicts a hinge motion that flattens basic surfaces on each monomer that flank the dimer interface, which suggests a reversible association between the FAC1 globular catalytic domain and intracellular membranes, with N-terminal transmembrane and disordered linker regions serving as the anchor and attachment to the globular catalytic domain, respectively.
Han
Byung Woo
BW
Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA.
Bingman
Craig A
CA
Mahnke
Donna K
DK
Bannen
Ryan M
RM
Bednarek
Sebastian Y
SY
Sabina
Richard L
RL
Phillips
George N
GN
D000659:AMP Deaminase / Q000737:chemistry* / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000502:physiology*; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism*; D018360:Crystallography, X-Ray; D007313:Insecta; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid
D029681:Arabidopsis Proteins; D000659:AMP Deaminase; C503078:FAC1 protein, Arabidopsis