Pseudo-merohedral Twinning and Noncrystallographic Symmetry in Orthorhombic Crystals of SIVmac239 Nef Core Domain Bound to Different-length TCR Fragments
HIV/SIV Nef mediates many cellular processes through interactions with various cytoplasmic and membrane-associated host proteins, including the signalling subunit of the T-cell receptor (TCR{zeta}). Here, the crystallization strategy, methods and refinement procedures used to solve the structures of the core domain of the SIVmac239 isolate of Nef (Nef{sub core}) in complex with two different TCR{zeta} fragments are described. The structure of SIVmac239 Nef{sub core} bound to the longer TCR{zeta} polypeptide (Leu51-Asp93) was determined to 3.7 {angstrom} resolution (R{sub work} = 28.7%) in the tetragonal space group P4{sub 3}2{sub 1}2. The structure of SIVmac239 Nef{sub core} in complex with the shorter TCR{zeta} polypeptide (Ala63-Arg80) was determined to 2.05 {angstrom} resolution (R{sub work} = 17.0%), but only after the detection of nearly perfect pseudo-merohedral crystal twinning and proper assignment of the orthorhombic space group P2{sub 1}2{sub 1}2{sub 1}. The reduction in crystal space-group symmetry induced by the truncated TCR{zeta} 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 P2{sub 1}2{sub 1}2{sub 1} crystal form to pseudo-merohedral twinning.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- DOE - OFFICE OF SCIENCE
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 1019650
- Report Number(s):
- BNL-95496-2011-JA; TRN: US201115%%290
- Journal Information:
- Acta Crystallographica Section D: Biological Crystallography, Vol. 66, Issue 2; ISSN 0907-4449
- Country of Publication:
- United States
- Language:
- English
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