Crystallization and preliminary X-ray diffraction analysis of human dipeptidyl peptidase 10 (DPPY), a component of voltage-gated potassium channels

Abstract

Dipeptidyl peptidase 10 (DPP10, DPPY) is an inactive peptidase associated with voltage-gated potassium channels, acting as a modulator of their electrophysiological properties, cell-surface expression and subcellular localization. Because potassium channels are important disease targets, biochemical and structural characterization of their interaction partners was sought. DPP10 was cloned and expressed using an insect-cell system and the protein was purified via His-tag affinity and size-exclusion chromatography. Crystals obtained by the sitting-drop method were orthorhombic, belonging to space group P2(1)2(1)2(1) with unit-cell parameters a = 80.91, b = 143.73, c = 176.25 Å. A single solution with two molecules in the asymmetric unit was found using the structure of DPP6 (also called DPPX; PDB entry 1xfd) as the search model in a molecular replacement protocol.

Figure 1

Sequence alignment of DPP10, DPP4 and DPP6 showing the region around the consensus sequence (GXSXG). The arrow emphasises the substitution of the catalytic serine in DPP4 by glycine in DPP10 and by aspartic acid in DPP6. The alignment was generated with ClustalW (Larkin et al., 2007; Goujon et al., 2010 ▶). The colouring scheme distinguishes hydrophobic (red), polar (green), negatively charged (blue) and positively charged (magenta) residues. Asterisks indicate identical residues, whereas colons denote highly similar residues and periods denote less similar residues with respect to physicochemical properties.

Figure 2

Crystal of DPP10 with approximate dimensions of 0.2 × 0.01 × 0.01 mm grown using the sitting-drop vapour-diffusion method at 293 K.

Figure 3

Diffraction pattern of DPP10. The inset shows the high-resolution limit of the data set. The figure was generated using the program ADXV (http://www.scripps.edu/~arvai/adxv.html).