Crystal structure of the oligomerization domain of NSP4 from rotavirus reveals a core metal-binding site.
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 (NSP4(114-135)) 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 (NSP4(95-137)). NSP4(95-137) 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.
Bowman
G D
GD
Department of Molecular Biology, Lewis Thomas Laboratories, Princeton University, Princeton, NJ 08544, USA.
Nodelman
I M
IM
Levy
O
O
Lin
S L
SL
Tian
P
P
Zamb
T J
TJ
Udem
S A
SA
Venkataraghavan
B
B
Schutt
C E
CE
D000595:Amino Acid Sequence; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D018360:Crystallography, X-Ray; D006023:Glycoproteins / Q000737:chemistry* / Q000378:metabolism*; D006860:Hydrogen Bonding; D008274:Magnesium / Q000378:metabolism; D008670:Metals / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D012401:Rotavirus / Q000737:chemistry*; D016415:Sequence Alignment; D013324:Strontium / Q000378:metabolism; D014118:Toxins, Biological; D017361:Viral Nonstructural Proteins / Q000737:chemistry* / Q000378:metabolism*; D014867:Water / Q000378:metabolism
D006023:Glycoproteins; D008670:Metals; C081369:NS28 protein, rotavirus; D014118:Toxins, Biological; D017361:Viral Nonstructural Proteins; D014867:Water; D008274:Magnesium; D002118:Calcium; D013324:Strontium