THREE-DIMENSIONAL STRUCTURE OF CYTOKINES, RECEPTORS AND IMMUNE SYSTEM PROTEINS

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1) The crystal structure of the multifunctional cytokine, Transforming Growth Factor-beta (TGF-beta 2), has now been refined to 1.8A resolution. The molecule is a homodimer, with each subunit having an unusual open fold with a preserved disulfide-rich core. Comparison with other members of the TGF-beta family and with the members of the superfamily such as activins and inhibins indicate that they probably adopt very similar structures. The folding topology is also similar to that adopted by Nerve Growth Factor (NGF), and of Platelet Derived Growth Factor (PDGF), although the mode of dimer formation is quite different for all three proteins. 2) As part of an investigation of the structural basis of antibody specificity, the crystal structure of the complex of the MAB HyHEL-5 with chicken lysozyme has been refined. Also, the structure of the complex of this antibody with a mutant lysozyme with 10,000 times weaker binding has been determined. In the mutant an arginine present in the wild type has been replaced by a lysine (R68K). A comparison of the mutant and the wild type has been made in order to explain the large effect of this conservative mutation on the affinity.