Herbaspirillum seropedicae signal transduction protein PII is structurally similar to the enteric GlnK

Abstract

PII-like proteins are signal transduction proteins found in bacteria, archaea and eukaryotes. They mediate a variety of cellular responses. A second PII-like protein, called GlnK, has been found in several organisms. In the diazotroph Herbaspirillum seropedicae, PII protein is involved in sensing nitrogen levels and controlling nitrogen fixation genes. In this work, the crystal structure of the unliganded H. seropedicae PII was solved by X-ray diffraction. H. seropedicae PII has a Gly residue, Gly108 preceding Pro109 and the main-chain forms a b turn. The glycine at position 108 allows a bend in the C-terminal main-chain, thereby modifying the surface of the cleft between monomers and potentially changing function. The structure suggests that the C-terminal region of PII proteins may be involved in specificity of function, and nonenteric diazotrophs are found to have the C-terminal consensus XGXDAX(107-112). We are also proposing binding sites for ATP and 2-oxoglutarate based on the structural alignment of PII with PII-ATP/ GlnK-ATP, 5-carboxymethyl-2-hydroxymuconate isomerase and 4-oxalocrotonate tautomerase bound to the inhibitor 2-oxo-3-pentynoate.

Crystal structures of the signal transducing protein GlnK from Thermus thermophilus HB8

“…The trimer formation is essentially similar to those of the GlnK (Xu et al, 1998) and GlnB structures (Cheah et al, 1994;Machado Benelli et al, 2002;Xu et al, 2003) and is consistent with the sedimentation equilibrium analysis results, which suggested that T. thermophilus GlnK behaves as a trimer in solution. In form Ib, the molecular surface area of molecule A is 7754 Å 2 , in which 31% (2380 Å 2 ) of the surface area facing molecules B and C is buried.…”

“…The GlnB crystal structures from E. coli, Herbaspirillum seropedicae, and the cyanobacteria Synechococcus and Synechocystis, as well as the structure of GlnK from E. coli, have been reported (Cheah et al, 1994;Machado Benelli et al, 2002;Xu et al, 1998Xu et al, , 2003. The GlnB and GlnK structures are quite similar, and they share the Tloop, the B-loop, and the C-loop, which are assumed to be functionally important (Cheah et al, 1994;Xu et al, 1998).…”

Crystal Structure of the Cyanobacterial Signal Transduction Protein PII in Complex with PipX

“…2 P II proteins sense carbon-related, nitrogen-related, and energy-related signals, and interact with diverse target proteins, most of which are involved in the regulation of nitrogen metabolism. A series of structures of P II proteins from bacteria, [3][4][5][6][7] archaea, 8 and plants 9 have been solved. All exist as trimers, with each subunit sharing a highly similar core structure of an antiparallel β-sheet and two α-helices at the lateral surface.…”

Crystal structures of the apo and ATP bound Mycobacterium tuberculosis nitrogen regulatory PII protein

“…The C-terminal residues extend out from the b4 strand to form a C-loop (Asp97 to Leu112) and has a 3 10 helix embedded within it between Gly108 and Ala111, consistent with other PII like protein structures. 16,24,[30][31][32][33][34][35] Structure of the ATP bound Mtb PII protein…”