Structure And Function Research On DHBPs From Streptococcus Pneumoniae

PurposeRiboflavin as we called vitamin B12 generally,is the precursor of cofactor flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN),which has crucial function in the procession of biosynthesis for organisms.Research has showed that gram-positive bacteria such as S.Pneumoniae, gram-negative bacteria as Salmonella typhimurium and fungi like Candida albicans need to autosynthesis riboflavin to maintain their survival and proliferation if they haven't obtain flavin from the surroundings.3,4-Dihydroxy-2-butanone-4-phosphate synthase (DHBPs) is one of the key enzymes in the biosynthesis of riboflavin. With the activation of Mg²⁺,DHBPs can act on ribulose-5-phosphate (Ru5P )and decompose it to formate and 3,4-dihydroxy-2-butanone-4-phosphate which is one of the necessary materials. Therefore, we can inhabit the activity of DHBPs, we may block the biosynthesis of riboflavin and then we may suppress bacterial survival and proliferation.Human don't have the enzymes related to the biosynthesis of riboflavin and we must obtain it from food to meet our survival needs. Thus, three-dimensional structures of the riboflavin related enzymes which may be the antimicrobial effect affecting points can provide important structure models for the design and development of new generation antimicrobial agents. Hence, DHBPs has the potential to be the target protein for the new antibiotic.On account of the trend that the drug resistance more and more serious in S. Pneumoniae infection, it is extremely urgent to develop structure-based antibiotics.Our research aim at provide theoretical basis to the potential new generation antibiotics via the analysis the structure of the S. Pneumoniae DHBPs.Method:We collected the data of the crystal structure of DHBPs from Streptococcus Pneumoniae by a house X ray as light source followed by the cloning , purification and gas-liquid diffusion method crystallization . We got the 3-dimensional structure of DHBPs by the method of molecule-displace (MR) with the structure of Candida albicans ( PDB code 10.2210 ) as a model .Conclusion:We obtained one set of data with the resolution was 2.21-2.20? and amended the structure .The overall architecture of DHBP is similar to other known DHBPs from other species, which are structurally conserved. Gel filtration experiment haved suggested that the protein was arranged as a dimer in solution, conforming to the polymerization form of dimer in the crystals. Structure and sequence consered analysis suggest the binding sites of DHBPs and the substrate Ru5P. Residues , including Arg139, Thr143 and His142, directly participate the binding of DHBPs to the phosphate group of Ru5P, and amino acids Glu30, Asp32, Cys57, Glu163, Thr96, His125 and Asp90, directly bind to the ribulose group of Ru5P. In addition, Leu55 and Phe85 provide the hydrophobic environment for the binding of enzyme and its substrate.Thus, it will supply a theoretical basis for the new general antibiocs.