Computational design and crystal structure of an enhanced affinity mutant human CD8 alphaalpha coreceptor.
Human CD8 is a T cell coreceptor, which binds to pHLA I and plays a pivotal role in the activation of cytotoxic T lymphocytes. Soluble recombinant CD8 alphaalpha has been shown to antagonize T cell activation, both in vitro and in vivo. However, because of a very low affinity for pHLA I, high concentrations of soluble CD8 alphaalpha are required for efficient inhibition. Based upon our knowledge of the wild-type CD8/pHLA I structure, we have designed and produced a mutated form of soluble CD8 alphaalpha that binds to pHLA I with approximately fourfold higher affinity. We have characterized the binding of the high affinity CD8 mutant using surface plasmon resonance and determined its structure at 2.1 A resolution using X-ray crystallography. The analysis of this structure suggests that the higher affinity is achieved by providing a larger side chain that allows for an optimal contact to be made between the HLA alpha3 loop and the mutated CDR-like loops of CD8.
Cole
David K
DK
Nuffield Department of Clinical Medicine, John Radcliffe Hospital, Oxford University, Oxford, United Kingdom.
Rizkallah
Pierre J
PJ
Boulter
Jonathan M
JM
Sami
Malkit
M
Vuidepot
Anne-lise
AL
Glick
Meir
M
Gao
Feng
F
Bell
John I
JI
Jakobsen
Bent K
BK
Gao
George F
GF
D019943:Amino Acid Substitution; D016827:CD8 Antigens / Q000737:chemistry* / Q000235:genetics*; D019295:Computational Biology; D003198:Computer Simulation; D003460:Crystallization; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D015202:Protein Engineering / Q000379:methods; D017510:Protein Folding; D020349:Surface Plasmon Resonance
D016827:CD8 Antigens; C409469:CD8 antigen, alpha chain