Structural analyses of Legionella LepB reveal a new GAP fold that catalytically mimics eukaryotic RasGAPYu, Q., Hu, L., Yao, Q., Zhu, Y., Dong, N., Wang, D.-C., Shao, F.
(2013) Cell Res 23: 775-787
- PubMed: 23588383
- DOI: https://doi.org/10.1038/cr.2013.54
- Primary Citation of Related Structures:
- PubMed Abstract:
Rab GTPases are emerging targets of diverse bacterial pathogens. Here, we perform biochemical and structural analyses of LepB, a Rab GTPase-activating protein (GAP) effector from Legionella pneumophila. We map LepB GAP domain to residues 313-618 and show that the GAP domain is Rab1 specific with a catalytic activity higher than the canonical eukaryotic TBC GAP and the newly identified VirA/EspG family of bacterial RabGAP effectors. Exhaustive mutation analyses identify Arg444 as the arginine finger, but no catalytically essential glutamine residues. Crystal structures of LepB313-618 alone and the GAP domain of Legionella drancourtii LepB in complex with Rab1-GDP-AlF3 support the catalytic role of Arg444, and also further reveal a 3D architecture and a GTPase-binding mode distinct from all known GAPs. Glu449, structurally equivalent to TBC RabGAP glutamine finger in apo-LepB, undergoes a drastic movement upon Rab1 binding, which induces Rab1 Gln70 side-chain flipping towards GDP-AlF3 through a strong ionic interaction. This conformationally rearranged Gln70 acts as the catalytic cis-glutamine, therefore uncovering an unexpected RasGAP-like catalytic mechanism for LepB. Our studies highlight an extraordinary structural and catalytic diversity of RabGAPs, particularly those from bacterial pathogens.
National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.