Volume 23, No 6, Jun 2013
ISSN: 1001-0602
EISSN: 1748-7838 2018
impact factor 17.848*
(Clarivate Analytics, 2019)
Volume 23 Issue 6, June 2013: 775-787
ORIGINAL ARTICLES
Structural analyses of Legionella LepB reveal a new GAP fold that catalytically mimics eukaryotic RasGAP
Qin Yu1,2,4,*, Liyan Hu2,*, Qing Yao2,*, Yongqun Zhu3, Na Dong2, Da-Cheng Wang1 and Feng Shao2
1National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
2National Institute of Biological Sciences, #7 Science Park Rd, Zhongguancun Life Science Park, Beijing 102206, China
3Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China
4Graduate University of Chinese Academy of Sciences, Beijing 100049, China
Correspondence: Feng Shao, Tel: +86-10-80728593; Fax: +86-10-80728046 E-mail: shaofeng@nibs.ac.cn; Na Dong, E-mail: dongna@nibs.ac.cn; Da-Cheng Wang,(dcwang@ibp.ac.cn)
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.
10.1038/cr.2013.54
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