Staphylococcus aureusthiaminase II: oligomerization warrants proteolytic protection against serine proteases

Abstract

Staphylococcus aureusTenA (SaTenA) is a thiaminase type II enzyme that catalyzes the deamination of aminopyrimidine, as well as the cleavage of thiamine into 4-amino-5-hydroxymethyl-2-methylpyrimidine (HMP) and 5-(2-hydroxyethyl)-4-methylthiazole (THZ), within thiamine (vitamin B1) metabolism. Further, by analogy with studies ofBacillus subtilisTenA,SaTenA may act as a regulator controlling the secretion of extracellular proteases such as the subtilisin type of enzymes in bacteria. Thiamine biosynthesis has been identified as a potential drug target of the multi-resistant pathogenS. aureusand therefore all enzymes involved in theS. aureusthiamine pathway are presently being investigated in detail. Here, the structure ofSaTenA, determined by molecular replacement and refined at 2.7 Å resolution to anRfactor of 21.6% with one homotetramer in the asymmetric unit in the orthorhombic space groupP212121, is presented. The tetrameric state of wild-type (WT)SaTenA was postulated to be the functional biological unit and was confirmed by small-angle X-ray scattering (SAXS) experiments in solution. To obtain insights into structural and functional features of the oligomericSaTenA, comparative kinetic investigations as well as experiments analyzing the structural stability of the WTSaTenA tetramerversusa monomericSaTenA mutant were performed.