8WM7

Cryo-EM structure of cyanobacterial nitrate/nitrite transporter NrtBCD in complex with signalling protein PII

Summary for 8WM7

• Entry DOI: 10.2210/pdb8wm7/pdb
• Related: 8W9M 8WM8
• EMDB information: 37644
• Descriptor: Nitrate transport permease protein, Nitrate transport ATP-binding protein, Nitrogen regulatory protein P-II, ... (5 entities in total)
• Functional Keywords: atp-dependent transporter, abc transporter, nitrate/nitrite transporter, membrane protein
• Biological source: Nostoc sp.; More
• Total number of polymer chains: 7
• Total formula weight: 210845.58

Authors

Li, B.,Zhou, C.Z.,Chen, Y.X.,Jiang, Y.L. (deposition date: 2023-10-03, release date: 2024-02-28, Last modification date: 2024-03-20)

Primary citation

Li, B.,Wang, X.Q.,Li, Q.Y.,Xu, D.,Li, J.,Hou, W.T.,Chen, Y.,Jiang, Y.L.,Zhou, C.Z.
Allosteric regulation of nitrate transporter NRT via the signaling protein PII.
Proc.Natl.Acad.Sci.USA, 121:e2318320121-e2318320121, 2024

PubMed Abstract: Coordinated carbon and nitrogen metabolism is crucial for bacteria living in the fluctuating environments. Intracellular carbon and nitrogen homeostasis is maintained by a sophisticated network, in which the widespread signaling protein PII acts as a major regulatory hub. In cyanobacteria, PII was proposed to regulate the nitrate uptake by an ABC (ATP-binding cassette)-type nitrate transporter NrtABCD, in which the nucleotide-binding domain of NrtC is fused with a C-terminal regulatory domain (CRD). Here, we solved three cryoelectron microscopy structures of NrtBCD, bound to nitrate, ATP, and PII, respectively. Structural and biochemical analyses enable us to identify the key residues that form a hydrophobic and a hydrophilic cavity along the substrate translocation channel. The core structure of PII, but not the canonical T-loop, binds to NrtC and stabilizes the CRD, making it visible in the complex structure, narrows the substrate translocation channel in NrtB, and ultimately locks NrtBCD at an inhibited inward-facing conformation. Based on these results and previous reports, we propose a putative transport cycle driven by NrtABCD, which is allosterically inhibited by PII in response to the cellular level of 2-oxoglutarate. Our findings provide a distinct regulatory mechanism of ABC transporter via asymmetrically binding to a signaling protein.

PubMed: 38457518
DOI: 10.1073/pnas.2318320121

Experimental method

ELECTRON MICROSCOPY (3.53 Å)