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The N-acetylglutamate kinase from Streptococcus mutans was expressed in Escherichia coli in soluble form and purified to homogeneity. Crystals suitable for X-ray diffraction were obtained by hanging-drop vapor diffusion method and diffracted to 2.06 Å. The crystal belonged to space group P21212, with unit cell parameters a 57.19 Å, b 94.76 Å, c 47.58 Å. The gel filtration and initial phasing results showed that the enzyme exists as a monomer, which is different from previously reported N-acetylglutamate kinases.

The thrC gene of Streptococcus mutans encodes threonine synthase, which is a potential target for drug design. To study the structure and function of the enzyme, the thrC gene was amplified from Streptococcus mutans genomic DNA and cloned into the expression vector pET28. The protein was expressed in Escherichia coli in soluble form and purified to homogeneity. Crystals suitable for X-ray diffraction were obtained by hanging-drop vapor diffusion method. The crystal diffracted to 2.5 Å and belonged to space group P31 or P32, with unit cell parameters ab60.39 Å, c118.62 Å.

B. subtilis dihydroorotase is an important enzyme in de novo pyrimidine biosynthesis pathway and encoded by pyrC gene in pyr operon. pyrC was amplified from B. subtilis genomic DNA and cloned into expression vector pET21- DEST. Dihydroorotase was expressed soluble form in E. coli and purified. The protein was crystallized and diffracted to 2.2 Å. The crystal belongs to P212121 space-group, with unit cell parameters a=48.864Å, b=84.99Å, c=203.05Å. There are 2 molecules per asymmetry unit.

The smu.134 gene encodes a putative transcriptional regulator of 217 residues in Streptococcus mutans, a major pathogen for human dental caries. The gene was cloned into expression vector pET28?? and expressed in soluble form in E. coli strain BL21 (DE3) with a His tag at its N-terminus. The recombinant protein SMU.134 was purified to homogeneity in a two step procedure of Ni2 chelating and size exclusion chromatography. Crystals suitable for X-ray diffraction were obtained by hanging-drop vapor diffusion method and diffracted to 2.6 Å. The crystal belonged to space group P212121, with unit-cell parameters a55.03 Å, b80.84 Å, c107.96 Å.

Smu.1392c is a protein with 158 residues of uncharacterized function. Bioinformatics studies predict it is a putative acetyltransferase. In order to identify its exact function via structural studies, Smu.1392c gene was amplified from Streptococcus mutans genomic DNA and cloned into expression vector PET28a. Smu.1392c was crystallized and diffracted to a resolution of 3 Å in-house. The crystal belongs to R32 space group, with unit cell parameters a b 229.10, c 63.49 Å. There are 2 or 3 molecules in the asymmetric unit.

B. subtilis YjbK is a protein with 190 residues of uncharacterized function, it has been annotated by Pfam database as a member of adenylate cyclase family (EC: 4.6.1.1). In order to identify its exact function via structural studies, yjbK gene was amplified from B. subtilis genomic DNA and cloned into expression vector pET21-DEST. The protein was expressed in a soluble form in E. coli and purified to homogeneity. YjbK was crystallized and diffracted to a resolution of 2.0 Å in-house. The crystals belong to P1 space group, with unit cell parameters a=32.38 Å, b=34.69 Å, c=46.02 Å, =96.560 , =99.683° , =111.333° . There is one molecule per asymmetric unit.