Pseudo-merohedral twinning and noncrystallographic symmetry in orthorhombic crystals of SIVmac239 Nef core domain bound to different-length TCRζ fragments
| Autor: | Alexander B. Sigalov, Walter M. Kim, Lawrence J. Stern |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2010 |
| Předmět: |
Models
Molecular Stereochemistry Molecular Sequence Data Receptors Antigen T-Cell Crystallography X-Ray Ligands Gene Products nef law.invention Crystal 03 medical and health sciences Tetragonal crystal system Structural Biology law pseudosymmetry T-cell receptor Protein Interaction Domains and Motifs Amino Acid Sequence Crystallization Protein Structure Quaternary 030304 developmental biology 0303 health sciences Crystallographic point group Nef human immunodeficiency virus Chemistry pseudo-merohedral twinning 030302 biochemistry & molecular biology Space group Hydrogen Bonding General Medicine Research Papers Peptide Fragments Crystallography noncrystallographic symmetry Orthorhombic crystal system Simian Immunodeficiency Virus Symmetry (geometry) Crystal twinning Protein Binding |
| Zdroj: | Acta Crystallographica Section D: Biological Crystallography |
| ISSN: | 1399-0047 0907-4449 |
| Popis: | P212121 crystals of SIV Nef core domain bound to a peptide fragment of the T-cell receptor ζ subunit exhibited noncrystallographic symmetry and nearly perfect pseudo-merohedral twinning simulating tetragonal symmetry. For a different peptide fragment, nontwinned tetragonal crystals were observed but diffracted to lower resolution. The structure was determined after assignment of the top molecular-replacement solutions to various twin or NCS domains followed by refinement under the appropriate twin law. HIV/SIV Nef mediates many cellular processes through interactions with various cytoplasmic and membrane-associated host proteins, including the signalling ζ subunit of the T-cell receptor (TCRζ). Here, the crystallization strategy, methods and refinement procedures used to solve the structures of the core domain of the SIVmac239 isolate of Nef (Nefcore) in complex with two different TCRζ fragments are described. The structure of SIVmac239 Nefcore bound to the longer TCRζ polypeptide (Leu51–Asp93) was determined to 3.7 Å resolution (R work = 28.7%) in the tetragonal space group P43212. The structure of SIVmac239 Nefcore in complex with the shorter TCRζ polypeptide (Ala63–Arg80) was determined to 2.05 Å resolution (R work = 17.0%), but only after the detection of nearly perfect pseudo-merohedral crystal twinning and proper assignment of the orthorhombic space group P212121. The reduction in crystal space-group symmetry induced by the truncated TCRζ polypeptide appears to be caused by the rearrangement of crystal-contact hydrogen-bonding networks and the substitution of crystallographic symmetry operations by similar noncrystallographic symmetry (NCS) operations. The combination of NCS rotations that were nearly parallel to the twin operation (k, h, −l) and a and b unit-cell parameters that were nearly identical predisposed the P212121 crystal form to pseudo-merohedral twinning. |
| Databáze: | OpenAIRE |
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