2J9C: Structure Of Glnk1 With Bound Effectors Indicates Regulatory Mechanism For Ammonia Uptake

A binary complex of the ammonia channel Amt1 from Methanococcus jannaschii and its cognate P(II) signalling protein GlnK1 has been produced and characterized. Complex formation is prevented specifically by the effector molecules Mg-ATP and 2-ketoglutarate. Single-particle electron microscopy of the complex shows that GlnK1 binds on the cytoplasmic side of Amt1. Three high-resolution X-ray structures of GlnK1 indicate that the functionally important T-loop has an extended, flexible conformation in the absence of Mg-ATP, but assumes a compact, tightly folded conformation upon Mg-ATP binding, which in turn creates a 2-ketoglutarate-binding site. We propose a regulatory mechanism by which nitrogen uptake is controlled by the binding of both effector molecules to GlnK1. At normal effector levels, a 2-ketoglutarate molecule binding at the apex of the compact T-loop would prevent complex formation, ensuring uninhibited ammonia uptake. At low levels of Mg-ATP, the extended loops would seal the ammonia channels in the complex. Binding of both effector molecules to P(II) signalling proteins may thus represent an effective feedback mechanism for regulating ammonium uptake through the membrane.
PDB ID: 2J9CDownload
MMDB ID: 53716
PDB Deposition Date: 2006/11/7
Updated in MMDB: 2007/10
Experimental Method:
x-ray diffraction
Resolution: 1.3  Å
Source Organism:
Similar Structures:
Biological Unit for 2J9C: trimeric; determined by author and by software (PQS)
Molecular Components in 2J9C
Label Count Molecule
Proteins (3 molecules)
Hypothetical Nitrogen Regulatory Pii-like Protein Mj0059(Gene symbol: MJ_RS00300)
Molecule annotation
Chemicals (17 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB