CRYSTAL PACKING INTERACTIONS IN STREPTAVIDIN CRYSTALS. Ronald E. Stenkamp, Stefanie Freitag, Isolde Le Trong, Ashutosh Chilkoti and Patrick S. Stayton, Dept. of Biological Structure and Center for Bioengineering, University of Washington, Seattle, WA 98195

The high-affinity streptavidin-biotin interaction is widely used in biotechnologies such as bioseparations and diagnostics. This interaction makes streptavidin and biotin prime candidates for structural and functional studies of protein-ligand interactions, but streptavidin's ability to crystallize in a number of three- dimensional and two-dimensional crystal forms [1,2,3,4,5] might also provide a mechanism for the design of biomaterials with specific inter-molecular spacings and orientations. For example, streptavidin is being investigated as a potential two-dimensional crystalline substrate for electron microscopic studies of other biological macromolecules. To provide a basis for the design of mutated streptavidin molecules with different packing characteristics, we are examining the crystal packing interactions in the various crystal forms available to date. We will determine which residues are most commonly involved in the inter-tetramer interfaces and locate potential regions on the protein surface suitable for mutagenesis studies aimed at modulating the crystal packing and growth properties of the protein.

This work is supported by NIH grant DK49655.

[1]. Pahler et al., J. Biol. Chem. (1987) 262, 13933-13937.

[2]. Hendrickson et al., Proc. Natl. Acad. Sci. USA (1989) 86, 2190-2194.

[3]. Weber et al., Science (1989) 243, 85-88.

[4]. Hemming et al., J. Mol. Biol. (1995) 246, 308-316.

[5]. Avila-Sakar and Chiu, Biophysical J. (1996) 70, 57-68.