Structural highlights
FunctionPublication Abstract from PubMedPurification of suitable quantity of homogenous protein is very often the bottleneck in protein structural studies. Overexpression of a desired gene and attachment of enzymatically cleavable affinity tags to the protein of interest made a breakthrough in this field. Here we describe the structure of Galleria mellonella silk proteinase inhibitor 2 (GmSPI-2) determined both by X-ray diffraction and NMR spectroscopy methods. GmSPI-2 was purified using a new method consisting in non-enzymatic His-tag removal based on a highly specific peptide bond cleavage reaction assisted by Ni(II) ions. The X-ray crystal structure of GmSPI-2 was refined against diffraction data extending to 0.98 A resolution measured at 100 K using synchrotron radiation. Anisotropic refinement with the removal of stereochemical restraints for the well-ordered parts of the structure converged with R factor of 10.57% and Rfree of 12.91%. The 3D structure of GmSPI-2 protein in solution was solved on the basis of 503 distance constraints, 10 hydrogen bonds and 26 torsion angle restraints. It exhibits good geometry and side-chain packing parameters. The models of the protein structure obtained by X-ray diffraction and NMR spectroscopy are very similar to each other and reveal the same beta2alphabeta fold characteristic for Kazal-family serine proteinase inhibitors. Atomic resolution structure of a protein prepared by non-enzymatic His-tag removal. Crystallographic and NMR study of GmSPI-2 inhibitor.,Kopera E, Bal W, Lenarcic Zivkovic M, Dvornyk A, Kludkiewicz B, Grzelak K, Zhukov I, Zagorski-Ostoja W, Jaskolski M, Krzywda S PLoS One. 2014 Sep 18;9(9):e106936. doi: 10.1371/journal.pone.0106936., eCollection 2014. PMID:25233114[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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