title: Computational design and crystal structure of an enhanced affinity mutant human CD8 alphaalpha coreceptor.
abstract: 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.
authors.affiliation: Nuffield Department of Clinical Medicine, John Radcliffe Hospital, Oxford University, Oxford, United Kingdom.
authors.forename: David K
authors.initials: DK
authors.lastname: Cole
authors.forename: Pierre J
authors.initials: PJ
authors.lastname: Rizkallah
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Boulter
authors.forename: Malkit
authors.initials: M
authors.lastname: Sami
authors.forename: Anne-lise
authors.initials: AL
authors.lastname: Vuidepot
authors.forename: Meir
authors.initials: M
authors.lastname: Glick
authors.forename: Feng
authors.initials: F
authors.lastname: Gao
authors.forename: John I
authors.initials: JI
authors.lastname: Bell
authors.forename: Bent K
authors.initials: BK
authors.lastname: Jakobsen
authors.forename: George F
authors.initials: GF
authors.lastname: Gao
mesh_terms: 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
chemical_list: D016827:CD8 Antigens; C409469:CD8 antigen, alpha chain