title: Molecular insights into plant cell proliferation disturbance by Agrobacterium protein 6b.
abstract: The Agrobacterium Ti plasmid (T-DNA) 6b proteins interact with many different host proteins implicated in plant cell proliferation. Here, we show that Arabidopsis plants overexpressing 6b display microRNA (miRNA) deficiency by directly targeting SERRATE and AGO1 via a specific loop fragment (residues 40-55). In addition, we report the crystal structures of Agrobacterium tumefaciens AK6b at 2.1 Å, Agrobacterium vitis AB6b at 1.65 Å, and Arabidopsis ADP ribosylation factor (ARF) at 1.8 Å. The 6b structure adopts an ADP-ribosylating toxin fold closely related to cholera toxin. In vitro ADP ribosylation analysis demonstrates that 6b represents a new toxin family, with Tyr 66, Thr 93, and Tyr 153 as the ADP ribosylation catalytic residues in the presence of Arabidopsis ARF and GTP. Our work provides molecular insights, suggesting that 6b regulates plant cell growth by the disturbance of the miRNA pathway through its ADP ribosylation activity.
authors.affiliation: Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore.
authors.forename: Meimei
authors.initials: M
authors.lastname: Wang
authors.forename: Takashi
authors.initials: T
authors.lastname: Soyano
authors.forename: Satoru
authors.initials: S
authors.lastname: Machida
authors.forename: Jun-Yi
authors.initials: JY
authors.lastname: Yang
authors.forename: Choonkyun
authors.initials: C
authors.lastname: Jung
authors.forename: Nam-Hai
authors.initials: NH
authors.lastname: Chua
authors.forename: Y Adam
authors.initials: YA
authors.lastname: Yuan
mesh_terms: D020727:ADP-Ribosylation Factors / Q000737:chemistry; D016960:Agrobacterium tumefaciens / Q000378:metabolism; D017360:Arabidopsis / Q000166:cytology / Q000254:growth & development / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000378:metabolism; D060565:Argonaute Proteins; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D001427:Bacterial Toxins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism; D049109:Cell Proliferation; D004269:DNA, Bacterial / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D035683:MicroRNAs / Q000378:metabolism; D016601:RNA-Binding Proteins; D000072099:Serrate-Jagged Proteins
chemical_list: C117457:AGO1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D060565:Argonaute Proteins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D002135:Calcium-Binding Proteins; D004269:DNA, Bacterial; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D035683:MicroRNAs; D016601:RNA-Binding Proteins; C000606277:SE protein, Arabidopsis; D000072099:Serrate-Jagged Proteins; C036483:T-DNA; D020727:ADP-Ribosylation Factors