Crystallization of two monoclonal Fab fragments of similar amino-acid sequence bound to the same area of horse cytochrome c and interacting by potentially distinct mechanisms.
The mouse monoclonal antibodies (mAb), 2E5.G10 and 1F5.D1, are specific for horse cytochrome c and appear to bind the same epitope, since their heavy (H) and light (L) chains are functionally interchangeable. Comparison of the amino-acid sequences suggests that slightly different interactions may be involved in antigen recognition. In addition, the H chains differ at only a few amino-acid residues from the H chain of a rat cytochrome c-specific mAb suggesting that specificity for one protein over another may be determined by these amino-acid differences. To address these possibilities, the three-dimensional structures of the Fab portions of the mAb bound to cytochrome c are being determined by X-ray diffraction analysis. Here we describe the preparation and crystallization of the two complexes with horse cytochrome c. The complex of the Fab fragment of 2E5.G10 with horse cytochrome c yielded crystals of X-ray diffraction quality under two sets of conditions; in both the space group was P2(1). The corresponding complex of 1F5.D1 under one of these conditions crystallized in the P2(1)2(1)2(1) space group. Three-dimensional X-ray data for these two complexes have been collected with nominal resolutions of 2.86 and 2.48 A, respectively.
Department of Microbiology, University of Minnesota, Minneapolis 55455, USA.
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Jemmerson
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Buron
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Sanishvili
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Margoliash
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Westbrook
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Westbrook