Bioinformatics and Expression Analysis of Pyridoxal Kinase in Vitamin B-6-producing Thermophilic Bacterium, Geobacillus sp. H6a

Abstract

Pyridoxal kinase (pdxK) catalyzes the phosphorylation of vitamin B-6 with ATP and divalent metal ions. The physical and chemical characteristics, biological structure and the function of pyridoxal kinase of Geobacillus sp. H6a (Gh) were studied using multiple bioinformatics tools. The full length of GhpdxK was 810 bp encoding a protein of 269 amino acids with a calculated molecular weight of 29.06 kDa and isoelectric point of 5.56. The function domain of GhpdxK showed a high confidence level with pyridoxal kinase domain, a member of ribokinase/pfkB-like superfamily domain. The predicted three-dimensional structure of GhpdxK was a homodimer and very similar to pdxK of Bacillus subtilis. The analysis of multiple sequence alignment and phylogenetic tree supported that GhpdxK shared high similarity with pdxK from Geobacillus spp. The GhpdxK expression pattern in culture condition and H₂O₂-induced oxidative stress were examined using RT-PCR. In the growth of Geobacillus sp. H6a, GhpdxK expression showed the highest expression level during the exponential phase. Under oxidative stress by hydrogen peroxide, GhpdxK expression significantly decreased but total extracellular vitamin B-6 was significantly increased compared to the control. This is the first time to study pyridoxal kinase in vitamin B-6 producing thermophilic bacterium.