Crystallographic analysis of the N-terminal domain of Middle East respiratory syndrome coronavirus nucleocapsid protein

Abstract

The N-terminal domain of the nucleocapsid protein from Middle East respiratory syndrome coronavirus (MERS-CoV NP-NTD) contains many positively charged residues and has been identified to be responsible for RNA binding during ribonucleocapsid formation by the virus. In this study, the crystallization and crystallographic analysis of MERS-CoV NP-NTD (amino acids 39-165), with a molecular weight of 14.7 kDa, are reported. MERS-CoV NP-NTD was crystallized at 293 K using PEG 3350 as a precipitant and a 94.5% complete native data set was collected from a cooled crystal at 77 K to 2.63 Å resolution with an overall Rmerge of 9.6%. The crystals were monoclinic and belonged to space group P21, with unit-cell parameters a = 35.60, b = 109.64, c = 91.99 Å, β = 101.22°. The asymmetric unit contained four MERS-CoV NP-NTD molecules.

Keywords: Middle East respiratory syndrome coronavirus; N-terminal domain; RNA binding; nucleocapsid protein.

Figure 1

SDS–PAGE analysis of MERS-CoV NP-NTD stained with Coomassie Brilliant Blue. Lane M, protein molecular-mass marker (labelled in kDa); lane 1, concentrated MERS-CoV NP-NTD after dialysis; lane 2, purified MERS-CoV NP-NTD.

Figure 2

Crystals of MERS-CoV NP-NTD obtained by the sitting-drop vapour-diffusion method. The largest crystals in the needle clusters are approximately 300 × 20 × 10 µm in size.

Figure 3

Typical X-ray diffraction pattern of MERS-CoV NP-NTD.