PT  - JOURNAL ARTICLE
AU  - Nikolaus Balthasar Dietz
AU  - Markus Huber
AU  - Isabel Sorg
AU  - Arnaud Goepfert
AU  - Alexander Harms
AU  - Tilman Schirmer
AU  - Christoph Dehio
TI  - Structural basis for selective targeting of Rac subfamily GTPases by a bacterial effector protein
AID  - 10.1101/2020.06.29.167221
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.06.29.167221
4099  - http://biorxiv.org/content/early/2020/07/02/2020.06.29.167221.short
4100  - http://biorxiv.org/content/early/2020/07/02/2020.06.29.167221.full
AB  - Ras-homology (Rho) family GTPases are conserved molecular switches controlling fundamental cellular activities in eukaryotic cells. As such, they are targeted by numerous bacterial toxins and effector proteins, which have been intensively investigated regarding their biochemical activities and discrete target spectra; however, molecular mechanisms of target selectivity have remained elusive. Here, we report a bacterial effector protein that targets all four Rac subfamily members of Rho family GTPases, but none of the closely related Cdc42 or RhoA subfamilies. This exquisite target selectivity of the FIC domain AMP-transferase Bep1 from Bartonella rochalimae is based on electrostatic interactions with a subfamily-specific pair of residues in the nucleotide-binding motif and the Rho insert helix. Residue substitutions at the identified positions in Cdc42 facilitate modification by Bep1, while corresponding Cdc42-like substitutions in Rac1 greatly diminish modification. Our study establishes a structural paradigm for target selectivity towards Rac subfamily GTPases and provides a highly selective tool for their functional analysis.Competing Interest StatementThe authors have declared no competing interest.