Download MendeleyN-terminal residues are crucial for quaternary structure and active site conformation for the phosphoserine aminotransferase from enteric human parasite E. histolytica.
Singh, R.K., Tomar, P., Dharavath, S., Kumar, S., Gourinath, S.(2019) Int J Biol Macromol 132: 1012-1023
- PubMed: 30959130
- DOI: https://doi.org/10.1016/j.ijbiomac.2019.04.027
- Primary Citation of Related Structures:
5YB0, 5YD2, 5YII - 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.
Organizational Affiliation:
Structural Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi 110067, India.
