Articles - Chemical Science & Engineering Research

Abstract

B-chains of the native selenophosphate synthetase (SPS) from strain K12 of E. coli (3U0OB) and of human SPS I (hSPSIB) was aligned with Swiss-Pdb Viewer and 24.8% identity was obtained with root mean square deviation (RMSD) of 1.48 Å. When aligned with Clustal Omega v.1.2.1, 3U0O B-chain truncated from the N-terminus till the 14^th AA with B-chain of 3FD6 truncated from the N-terminus till the 13^th AA, identity of 24.866% has been obtained for 93 AA. When hSPSIB and 3U0OB were aligned from the 1^st AA residue with Clustal Omega v.1.2.1, 22.892% identity based on 95 AA was received using 3FD5 and 3FD6 as a reference. The aforementioned points out that the N-termini of hSPSI and the SPS from E. coli are variable. The structural alignment of the chain with the active conformation (3FD6B) and 3U0OB obtained with YASARA View shows the same 32.57% identity but lesser RMSD of 1.630 Å than the chain in inactive conformation (3FD5B), a RMSD of 1.669 Å over 218 aligned residues, under other equal parameters. It has been proposed to consider hSPSI as a Ser/Thr hydrolase.

The labelling experiments on Mn-ATP binding using the concentrations of the reagents 10-times lower then usually, 3.7 mkM WT or 3.4 mkM C17S E197D recombinant SPS and radioactive Mn-[8-¹⁴C]ATP (0.5mM), have elucidated a right shoulder in the ATP-peak observed only with WT protein in the fractions eluted from the size-exclusive HPLC column. In the labelled protein peaks under enzyme turnover conditions, Mn-[8-¹⁴C]-AMP was bound to the SPS in the amount of 10% from the total ¹⁴C loaded.