24IO

Crystal structure of the RelSeq N-terminal domain from Streptococcus equisimilis in complex with pppGpp

Summary for 24IO

• Entry DOI: 10.2210/pdb24io/pdb
• Descriptor: Bifunctional (p)ppGpp synthase/hydrolase RelA, GLYCEROL, MANGANESE (II) ION, ... (6 entities in total)
• Functional Keywords: relseq, bifunctional enzyme, rela/spot homolog, stringent response, streptococcus equisimilis, alarmone, pppgpp, transferase
• Biological source: Streptococcus dysgalactiae subsp. equisimilis
• Total number of polymer chains: 2
• Total formula weight: 94788.86

Authors

Korban, S.A.,Kasatsky, P.S.,Spiridonova, Z.A.,Gurzhiy, V.V.,Paleskava, A.V.,Konevega, A.L.,Vinogradova, D.S. (deposition date: 2026-03-04, release date: 2026-03-18, Last modification date: 2026-07-29)

Primary citation

Korban, S.A.,Spiridonova, Z.A.,Kasatsky, P.S.,Shvetsov, A.V.,Gurzhiy, V.V.,Paleskava, A.,Kulminskaya, A.A.,Konevega, A.L.,Vinogradova, D.S.
Structural Basis of pppGpp Binding to the N-Terminal Domain of the Bifunctional RelA/SpoT Homolog Rel Seq : Crystal Structure and MD Analysis.
Int J Mol Sci, 27:-, 2026

PubMed Abstract: RelA/SpoT homologue family enzymes participate in controlling the cellular levels of the alarmone (p)ppGpp, thereby activating the stringent response and promoting survival under stress conditions. These proteins contain an N-terminal catalytic domain and a C-terminal regulatory domain. They catalyze both the synthesis of ppGpp/pppGpp from ATP and GDP/GTP and their hydrolysis to GDP/GTP and pyrophosphate. Here, we report the crystal structure of the N-terminal domain of Rel from in complex with pppGpp at 3.2 Å resolution. The asymmetric unit contains a dimer with asymmetric ligation: pppGpp occupies only the synthetase site in one monomer, whereas in the other monomer, it is bound in both the hydrolase and synthetase sites. The two monomers exhibit distinct conformational states, with pronounced rearrangements of the flexible loops surrounding the binding pockets, including the α2/α3 and α8/α9 loops that act as steric gates. Molecular dynamics simulations support the dual binding arrangement and reveal additional probable transient binding sites, including a region in the linker between hydrolase and synthetase subdomains. These findings provide a structural framework for understanding how pppGpp binding modulates the opposing catalytic activities of bifunctional Rel enzymes and suggest possible mechanisms for (p)ppGpp-mediated autoregulation.

PubMed: 42353222
DOI: 10.3390/ijms27125509

Experimental method

X-RAY DIFFRACTION (3.2 Å)