4OZN image
Deposition Date 2014-02-17
Release Date 2014-07-02
Last Version Date 2023-12-27
Entry Detail
PDB ID:
4OZN
Title:
GlnK2 from Haloferax mediterranei complexed with ATP
Biological Source:
Source Organism:
Host Organism:
Method Details:
Experimental Method:
Resolution:
2.60 Å
R-Value Free:
0.24
R-Value Work:
0.21
R-Value Observed:
0.21
Space Group:
P 31 2 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Molecule:Nitrogen regulatory protein P-II
Gene (Uniprot):glnK2
Chain IDs:A, B, C
Chain Length:143
Number of Molecules:3
Biological Source:Haloferax mediterranei
Primary Citation
The structure of a PII signaling protein from a halophilic archaeon reveals novel traits and high-salt adaptations.
Febs J. 281 3299 3314 (2014)
PMID: 24946894 DOI: 10.1111/febs.12881

Abstact

UNLABELLED To obtain insights into archaeal nitrogen signaling and haloadaptation of the nitrogen/carbon/energy-signaling protein PII, we determined crystal structures of recombinantly produced GlnK2 from the extreme halophilic archaeon Haloferax mediterranei, complexed with AMP or with the PII effectors ADP or ATP, at respective resolutions of 1.49 Å, 1.45 Å, and 2.60 Å. A unique trait of these structures was a three-tongued crown protruding from the trimer body convex side, formed by an 11-residue, N-terminal, highly acidic extension that is absent from structurally studied PII proteins. This extension substantially contributed to the very low pI value, which is a haloadaptive trait of H. mediterranei GlnK2, and participated in hexamer-forming contacts in one crystal. Similar acidic N-extensions are shown here to be common among PII proteins from halophilic organisms. Additional haloadaptive traits prominently represented in H. mediterranei GlnK2 are a very high ratio of small residues to large hydrophobic aliphatic residues, and the highest ratio of polar to nonpolar exposed surface for any structurally characterized PII protein. The presence of a dense hydration layer in the region between the three T-loops might also be a haloadaptation. Other unique findings revealed by the GlnK2 structure that might have functional relevance are: the adoption by its T-loop of a three-turn α-helical conformation, perhaps related to the ability of GlnK2 to directly interact with glutamine synthetase; and the firm binding of AMP, confirmed by biochemical binding studies with ATP, ADP, and AMP, raising the possibility that AMP could be an important PII effector, at least in archaea. DATABASE The atomic coordinates and structure factors have been deposited in the Protein Data Bank under the accession numbers 4OZL (hmGlnK2-AMP), 4OZJ (hmGlnK2-ADP), and 4OZN (hmGlnK2-ATP). STRUCTURED DIGITAL ABSTRACT hmGlnK2 and hmGlnK2 bind by x-ray crystallography (View interaction).

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