CRYSTALLIZATION AND PRELIMINARY-X-RAY DIFFRACTION STUDY OF AN IDIOTOPE-ANTI-IDIOTOPE FV-FV COMPLEX

A complex between the Fv fragment of an anti-hen eggwhite lysozyme antibody (D1.3) and the Fv fragment of an antibody specific for an idiotypic determinant of D1.3 has been crystallized in a form suitable for X-ray diffraction analysis. Both Fv fragments were expressed in soluble form in Escherichia coli and purified by affinity chromatography; diffraction-quality crystals were only obtained following separation of each Fv into distinct isoelectric forms. The crystals belong to space group C2, have unit cell dimensions a = 152.8 Angstrom, b = 79.4 Angstrom, c = 51.5 Angstrom, beta = 100.2 degrees, and diffract to better than 2.2 Angstrom resolution. The solvent content of the crystals is approximately 60% (v/v) with one Fv-Fv complex in the asymmetric unit. The ability to readily express both components of an antigen-antibody system in bacteria will allow us to rigorously assess the energetic contribution of individual amino acids to complex formation through pairwise mutagenesis of interacting residues.