Abstract
Carboxynorspermidine decarboxylase (CANSDC), which belongs to pyridoxal-5’-phosphate (PLP) dependent decarboxylase, exists in some species and involves in norspermidine biosynthesis. CANSDC of Helicobacter pylori (HpCANSDC), which is encoded by the gene nspC, contains 405 residues, and its putative function is decarboxylation of carboxynorspermidine to produce norspermidine. In this work, HpCANSDC was expressed and purified. We demonstrate that HpCANSDC is a dimer in the solution, with monomer molecular weight 47kDa. PEG3350 was used as main precipitate to grow HpCANSDC crystal. The crystals were diffracted to 2.6□, and the space group of HpCANSDC was P21 with unit cell parameters of a = 71.89 □, b = 84.12 □, c = 72.43 □, β = 113.17°. There are two molecules per asymmetry unit. Owing to no 3D structures of CANSDCs been published yet, other PLP-dependent decarboxylases, which sequences identity below 15%, were used as search models for molecular replacement method (MR). Meanwhile, the multiple-wavelength anomalous dispersion (MAD) method to was also used for phase determination. To carry out MAD method, the selenium derivative proteins (Se-HpCANSDC) was expressed and purified. (NH4)2SO4 was used as precipitate to grow the crystal. The crystals were diffracted to 2.1□, and the space group of Se-HpCANSDC was P21 with unit cell parameters of a = 86.74 □, b = 82.77 □, c = 118.17 □, β = 97.35°. There are four molecules per asymmetry unit.