Crystal structure of nonstructural protein 10 from the severe acute respiratory syndrome coronavirus reveals a novel fold with two zinc-binding motifs.
The severe acute respiratory syndrome coronavirus (SARS-CoV) possesses a large 29.7-kb positive-stranded RNA genome. The first open reading frame encodes replicase polyproteins 1a and 1ab, which are cleaved to generate 16 "nonstructural" proteins, nsp1 to nsp16, involved in viral replication and/or RNA processing. Among these, nsp10 plays a critical role in minus-strand RNA synthesis in a related coronavirus, murine hepatitis virus. Here, we report the crystal structure of SARS-CoV nsp10 at a resolution of 1.8 A as determined by single-wavelength anomalous dispersion using phases derived from hexatantalum dodecabromide. nsp10 is a single domain protein consisting of a pair of antiparallel N-terminal helices stacked against an irregular beta-sheet, a coil-rich C terminus, and two Zn fingers. nsp10 represents a novel fold and is the first structural representative of this family of Zn finger proteins found so far exclusively in coronaviruses. The first Zn finger coordinates a Zn2+ ion in a unique conformation. The second Zn finger, with four cysteines, is a distant member of the "gag-knuckle fold group" of Zn2+-binding domains and appears to maintain the structural integrity of the C-terminal tail. A distinct clustering of basic residues on the protein surface suggests a nucleic acid-binding function. Gel shift assays indicate that in isolation, nsp10 binds single- and double-stranded RNA and DNA with high-micromolar affinity and without obvious sequence specificity. It is possible that nsp10 functions within a larger RNA-binding protein complex. However, its exact role within the replicase complex is still not clear.
Joseph
Jeremiah S
JS
Department of Cell Biology, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, California 92037, USA.
Saikatendu
Kumar Singh
KS
Subramanian
Vanitha
V
Neuman
Benjamin W
BW
Brooun
Alexei
A
Griffith
Mark
M
Moy
Kin
K
Yadav
Maneesh K
MK
Velasquez
Jeffrey
J
Buchmeier
Michael J
MJ
Stevens
Raymond C
RC
Kuhn
Peter
P
D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017510:Protein Folding; D045473:Severe acute respiratory syndrome-related coronavirus; D017361:Viral Nonstructural Proteins / Q000737:chemistry* / Q000502:physiology; D016335:Zinc Fingers
C558878:Nsp10 protein, SARS virus; D017361:Viral Nonstructural Proteins