Multiple enzymatic activities of ParB/Srx superfamily mediate sexual conflict among conjugative plasmids

Abstract

Conjugative plasmids are typically locked in intergenomic and sexual conflicts with coresident rivals, whose translocation they block using fertility inhibition factors (FINs). We describe here the first crystal structure of an enigmatic FIN Osa deployed by the proteobacterial plasmid pSa. Osa contains a catalytically active version of the ParB/Sulfiredoxin fold with both ATPase and DNase activity, the latter being regulated by an ATP-dependent switch. Using the Agrobacterium tumefaciens VirB/D4 type-IV secretion system (T4SS), a relative of the conjugative T4SS, we demonstrate that catalytically active Osa blocks T-DNA transfer into plants. With a partially reconstituted T4SS in vitro, we show that Osa degrades T-DNA in the T-DNA-VirD2 complex prior to its translocation. Further, we present evidence for conservation and interplay between ATPase and DNase activities throughout the ParB/Sulfiredoxin fold, using other members of the family, namely P1 ParB and RK2 KorB, which have general functional implications across diverse biological contexts.

The sulfiredoxin–peroxiredoxin (Srx–Prx) axis in cell signal transduction and cancer development

“…Oncogenic suppressive activity or ‘Osa’ protein is probably a connecting link between ParB and Srx. Osa contains both DNAse [18] of ParB as well as ATPase domain of Srx [28]. In normal human tissues, Srx is present in kidney, lungs, and pancreas [29].…”

Tight control of genomic phosphorothioate modification by the ATP‐modulated autoregulation and reusability of DndB

“…). In addition to their involvement in DNA PT modification, members of the ParB/Srx superfamily are observed in diverse biological processes: (i) ParB, a component of the plasmid‐partitioning system (Par), is essential in bacterial chromosome segregation during cell division (Schumacher and Funnell, ; Chen et al ., ); (ii) Srx, a sulfinic acid reductase in eukaryotes, is functionally unrelated to ParB but is suggested to originate via truncation of ParB (Basu and Koonin, ; Jonsson et al ., ); (iii) Osa, the fertility inhibition protein, blocks T‐DNA transfer into plants (Maindola et al ., ); and (iv) some polymorphic toxin systems were found to fuse C‐terminally with ParB domains and likely function as nucleases (Zhang et al ., ). Notably, the highly conserved DGQHR motif in DndB consistently aligns well with the signature sequence of G(E/C)(R/H)RxxA (x represents any residue) in ParBs and Srxs (Fig. )…”

“…(Basu and Koonin, ). Further structural modeling of DndB using the Phyre2 server (http://www.sbg.bio.ic.ac.uk/~phyre/) showed that DndB residues G114 and R117 in the D 113 GQHR 117 motif correspond well to the active site residues in the ATP‐binding pockets of Srx (G97, R101) and Osa (G137, R140) (Maindola et al ., ), prompting us to test if these conserved sites might also support the ATPase activity of DndB (Fig. A).…”

SbnI is a free serine kinase that generates -phospho-l-serine for staphyloferrin B biosynthesis in

“…This fold has been described in a functionally diverse ParB/Srx superfamily of proteins. Members are found in varied biological contexts and thus far are described to bind a nucleotide for kinase, ATPase, or DNase activity (32,36). To our knowledge, no ParB/Srx family member has been found to be directly involved in siderophore biosynthesis.…”

“…SerK is a free serine kinase from T. kodakarensis that uses ADP to phosphorylate L-serine to generate OPS for cysteine biosynthesis. Of the proteins annotated in the ParB/Srx family, SerK is the only identified kinase, although Osa and Srx both possess ATPase activity (36,40). Overall, the structures of SerK The overall fold of SbnI(1-240) is shown as a schematic and divided into two domains with N and C termini and ␣-helices labeled.…”