3SPX

Crystal structure of O-Acetyl Serine Sulfhydrylase from Leishmania donovani

Summary for 3SPX

• Entry DOI: 10.2210/pdb3spx/pdb
• Related: 1Z7W 2PQM 2Q3C
• Descriptor: O-acetyl serine sulfhydrylase, CHLORIDE ION, SODIUM ION, ... (5 entities in total)
• Functional Keywords: o-acetyl serine sulfhydrylase, cysteine synthase, type ii plp dependent enzyme, cysteine biocynthesis, serine acetyl transferase, cytosolic, transferase
• Biological source: Leishmania donovani
• Total number of polymer chains: 1
• Total formula weight: 36071.81

Authors

Raj, I.,Gourinath, S. (deposition date: 2011-07-04, release date: 2012-07-04, Last modification date: 2025-03-26)

Primary citation

Raj, I.,Kumar, S.,Gourinath, S.
The narrow active-site cleft of O-acetylserine sulfhydrylase from Leishmania donovani allows complex formation with serine acetyltransferases with a range of C-terminal sequences
Acta Crystallogr.,Sect.D, 68:909-919, 2012

PubMed Abstract: Cysteine is a crucial substrate for the synthesis of glutathione and trypanothione, which in turn maintain intracellular redox homeostasis and defend against oxidative stress in the pathogen Leishmania donovani. Here, the identification, sequencing, characterization and crystal structure at 1.79 Å resolution of O-acetylserine sulfhydrylase (OASS), a cysteine-biosynthetic pathway enzyme from L. donovani (LdOASS), are reported. It shows binding to the serine acetyltransferase (SAT) C-terminal peptide, indicating that OASS and SAT interact with each other to form a cysteine synthase complex, further confirmed by the structure of LdOASS in complex with SAT C-terminal octapeptide at 1.68 Å resolution. Docking and fluorescence binding studies show that almost all SAT C-terminus mimicking tetrapeptides can bind to LdOASS. Some peptides had a higher binding affinity than the native peptide, indicating that SAT-OASS interactions are not sequence-specific. The structure of LdOASS with a designed peptide (DWSI) revealed that LdOASS makes more interactions with the designed peptide than with the native peptide. In almost all known SAT-OASS interactions the SAT C-terminal sequence was shown to contain amino acids with large side chains. Structural comparison with other OASSs revealed that LdOASS has a relatively less open active-site cleft, which may be responsible for its interaction with the smaller-amino-acid-containing C-terminal LdSAT peptide. Biochemical studies confirmed that LdOASS interacts with SATs from Entamoeba histolytica and Brucella abortus, further displaying its sequence-independent and versatile mode of interaction with SATs. This implicates a critical role of the size of the active-site cleft opening in OASS for SAT-OASS interaction and thus cysteine synthase complex formation.

PubMed: 22868756
DOI: 10.1107/S0907444912016459

Experimental method

X-RAY DIFFRACTION (1.79 Å)