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Solution Structure of the Carboxyl-Terminal Cysteine-Rich Domain of the VHv1.1 Polydnaviral Gene Product: Comparison with Other Cystine Knot Structural Folds†
journal contribution
posted on 2001-11-07, 00:00 authored by Jerrod Einerwold, Mahesh Jaseja, Kenneth Hapner, Bruce Webb, Valérie CopiéPolydnaviruses are an unusual group of insect viruses that have an obligate symbiotic association
with certain parasitic wasps. These viruses are transmitted with the wasp egg during oviposition into
lepidopteran insects, enabling the survival and development of the egg inside the host larvae. We report
the three-dimensional structure of a novel polydnaviral cysteine-rich motif (cys-motif), identified as the
carboxyl-terminal domain of a two cys-motif containing polydnaviral VHv1.1 gene product, abbreviated
“C-term VHv1.1”. This 65-residue domain was identified experimentally by limited proteolysis of the
full-length protein and was subsequently cloned in a bacterial expression system for NMR studies. The
C-term VHv1.1 3D structure was determined in solution by two-dimensional 1H NMR spectroscopy.
Calculation of the structure was based on a total of 300 upper distance restraints and 20 dihedral angle
constraints, and resulted in an ensemble of 25 representative conformers with an average rmsd of 0.47 Å
from the mean structure for core backbone atoms. The protein core is made of a four β-strand scaffold
held together in a compact structure by three disulfide bonds, which form a cystine knot. The four β-strands
are arranged in an unusual configuration to form a triple-stranded β-sheet and double-stranded β-sheet.
Comparison with other classes of cystine knots provides indication that C-term VHv1.1 represents a new
and distinct cytine knot motif. This analysis provides a structural basis for interpretation of the genetic
and amino acid sequence data classifying polydnavirus gene products as members of cysteine-rich protein
families.
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0.47 Å25 representative conformersNMR studiespolydnavirus gene productscystine knotsdistance restraints1 H NMR spectroscopypolydnaviral VHv 1.1 gene productlepidopteran insectsdisulfide bondscore backbone atomshost larvae20 dihedral angle constraintsacid sequence datacystine knotprotein coreinsect virusescytine knot motifexpression systemwasp eggstrandsolution Structure
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