title: Structural basis of Fic-mediated adenylylation.
abstract: The Fic family of adenylyltransferases, defined by a core HPFx(D/E)GN(G/K)R motif, consists of over 2,700 proteins found in organisms from bacteria to humans. The immunoglobulin-binding protein A (IbpA) from the bacterial pathogen Histophilus somni contains two Fic domains that adenylylate the switch1 tyrosine residue of Rho-family GTPases, allowing the bacteria to subvert host defenses. Here we present the structure of the second Fic domain of IbpA (IbpAFic2) in complex with its substrate, Cdc42. IbpAFic2-bound Cdc42 mimics the GDI-bound state of Rho GTPases, with both its switch1 and switch2 regions gripped by IbpAFic2. Mutations disrupting the IbpAFic2-Cdc42 interface impair adenylylation and cytotoxicity. Notably, the switch1 tyrosine of Cdc42 is adenylylated in the structure, providing the first structural view for this post-translational modification. We also show that the nucleotide-binding mechanism is conserved among Fic proteins and propose a catalytic mechanism for this recently discovered family of enzymes.
authors.affiliation: Department of Pharmacology, Howard Hughes Medical Institute, University of California, San Diego, La Jolla, California, USA.
authors.forename: Junyu
authors.initials: J
authors.lastname: Xiao
authors.forename: Carolyn A
authors.initials: CA
authors.lastname: Worby
authors.forename: Seema
authors.initials: S
authors.lastname: Mattoo
authors.forename: Banumathi
authors.initials: B
authors.lastname: Sankaran
authors.forename: Jack E
authors.initials: JE
authors.lastname: Dixon
mesh_terms: D000225:Adenine / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D055162:Biocatalysis; D016923:Cell Death; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D049452:Green Fluorescent Proteins / Q000378:metabolism; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008958:Models, Molecular; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D009711:Nucleotides / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D020764:cdc42 GTP-Binding Protein / Q000737:chemistry / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D020730:Guanine Nucleotide Dissociation Inhibitors; D050505:Mutant Proteins; D009711:Nucleotides; D011993:Recombinant Fusion Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D020764:cdc42 GTP-Binding Protein; D000225:Adenine