Structural and mutational analysis of TenA protein (HP1287) from the Helicobacter pylori thiamin salvage pathway – evidence of a different substrate specificity.

HP1287 ( tenA) from Helicobacter pylori is included among the genes that play a relevant role in bacterium colonization and persistence. The gene has been cloned and its product, protein TenA, has been expressed and purified. The crystal structures of the wild-type protein and the mutant F47Y have been determined at resolutions of 2.7 and 2.4 Å, respectively. The molecular model, a homotetramer with 222 symmetry, shows that the H. pylori TenA structure belongs to the thiaminase II class of proteins. These enzymes were recently found to be involved in a salvage pathway for the synthesis of the thiamin precursor hydroxypyrimidine, which constitutes a building block in thiamin biosynthesis, in particular in bacteria living in the soil. By contrast, enzymatic measurements on TenA from H. pylori indicate that the activity on the putative substrate 4-amino-5-aminomethyl-2-methylpyrimidine is very modest. Moreover, in the present study, we demonstrate that the mutation at residue 47, a position where a phenylalanine occurs in all the strains of H. pylori sequenced to date, is not sufficient to explain the very low catalytic activity toward the expected substrate. As a result of differences in the colonization environment of H. pylori as well as the TenA structural and catalytic peculiar features, we suggest a possible pivotal role for the H. pylori enzyme in the thiamin biosynthetic route, which is in agreement with the relevance of this protein in the stomach colonization process. Structured digital abstract • : TenA (uniprotkb: ) and TenA (uniprotkb: ) bind ( ) by x-ray crystallography ( ) [ABSTRACT FROM AUTHOR]