Crystal Structure of the Oligomerization Domain of NSP4 from Rotavirus Reveals a Core Metal-binding Site

• Published in: Journal of molecular biology Vol. 304; no. 5; pp. 861 - 871
• Main Authors: Bowman, Gregory D., Nodelman, Ilana M., Levy, Orlie, Lin, Shuo L., Tian, Peng, Zamb, Timothy J., Udem, Stephen A., Venkataraghavan, Babu, Schutt, Clarence E.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 15.12.2000
• Subjects: Amino Acid Sequence; Binding Sites; Calcium - metabolism; Crystallography, X-Ray; fusion; Glycoproteins - chemistry; Glycoproteins - metabolism; Hydrogen Bonding; Magnesium - metabolism; metal-binding protein; Metals - metabolism; Models, Molecular; Molecular Sequence Data; ns28; nsp4; NSP4 protein; parallel coiled-coil; Protein Structure, Quaternary; Protein Structure, Tertiary; Rotavirus; Rotavirus - chemistry; Sequence Alignment; Strontium - metabolism; Toxins, Biological; Viral Nonstructural Proteins - chemistry; Viral Nonstructural Proteins - metabolism; Water - metabolism; fusion; ns28; nsp4; rotavirus; parallel coiled-coil
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1006/jmbi.2000.4250

During the maturation of rotaviral particles, non-structural protein 4 (NSP4) plays a critical role in the translocation of the immature capsid into the lumen of the endoplasmic reticulum. Full-length NSP4 and a 22 amino acid peptide (NSP4114-135) derived from this protein have been shown to induce diarrhea in young mice in an age-dependent manner, and may therefore be the agent responsible for rotavirally-induced symptoms. We have determined the crystal structure of the oligomerization domain of NSP4 which spans residues 95 to 137 (NSP495-137). NSP495-137 self-associates into a parallel, tetrameric coiled-coil, with the hydrophobic core interrupted by three polar layers occupying a and d-heptad positions. Side-chains from two consecutive polar layers, consisting of four Gln123 and two of the four Glu120 residues, coordinate a divalent cation. Two independent structures built from MAD-phased data indicated the presence of a strontium and calcium ion bound at this site, respectively. This metal-binding site appears to play an important role in stabilizing the homo-tetramer, which has implications for the engagement of NSP4 as an enterotoxin.