5YII

Crystal Structure of 45 amino acid deleted from N-terminal of Phosphoserine Aminotransferase (PSAT) of Entamoeba histolytica

Summary for 5YII

• Entry DOI: 10.2210/pdb5yii/pdb
• Descriptor: Phosphoserine aminotransferase, THIOCYANATE ION (3 entities in total)
• Functional Keywords: delta45_ehpsat, transferase
• Biological source: Entamoeba histolytica
• Total number of polymer chains: 1
• Total formula weight: 35686.41

Authors

Singh, R.K.,Gourinath, S. (deposition date: 2017-10-04, release date: 2018-10-24, Last modification date: 2023-11-22)

Primary citation

Singh, R.K.,Tomar, P.,Dharavath, S.,Kumar, S.,Gourinath, S.
N-terminal residues are crucial for quaternary structure and active site conformation for the phosphoserine aminotransferase from enteric human parasite E. histolytica.
Int.J.Biol.Macromol., 132:1012-1023, 2019

PubMed Abstract: Phosphoserine aminotransferase (PSAT) is a pyridoxal-5'phosphate (PLP)-dependent enzyme that catalyzes the second reversible step in the phosphoserine biosynthetic pathway producing serine. The crystal structure of E. histolytica PSAT (EhPSAT) complexed with PLP was elucidated at 3.0 Å resolution and the structures of its mutants, EhPSAT_Δ45 and EhPSAT_Δ4, at 1.8 and 2.4 Å resolution respectively. Deletion of 45 N-terminal residues (EhPSAT_Δ45) resulted in an inactive protein, the structure showed a dimeric arrangement drastically different from that of the wild-type protein, with the two monomers translated and rotated by almost 180° with respect to each other; causing a rearrangement of the active site to which PLP was unable to bind. Deletion of first N-terminal 15 (EhPSAT_Δ15) and four 11th to 14th residues (EhPSAT_Δ4) yielded up to 98% and 90% decrease in the activity respectively. Absence of aldimine linkage between PLP-Lys in the crystal structure of EhPSAT_Δ4 mutant explains for such decrease in activity and describes the importance of these N-terminal residues. Furthermore, a halide-binding site was found in close proximity to the active site. A stretch of six amino acids (146-NNTIYG-151) only conserved in the Entamoeba genus, contributes to halide binding may explain that the halide inhibition could be specific to Entamoeba.

PubMed: 30959130
DOI: 10.1016/j.ijbiomac.2019.04.027

Experimental method

X-RAY DIFFRACTION (1.8 Å)