Three-dimensional structural model of the serine receptor ligand-binding domain.

Computer-based homology modeling techniques were used to construct a three-dimensional model of the Escherichia coli serine receptor ligand-binding domain based on the crystal structure of the Salmonella typhimurium aspartate receptor and the sequence homology between the two receptors. Residues that have been found in mutagenesis studies to be necessary for serine binding are located in a proposed serine-binding site. Several other mutations that affect swimming behavior require relatively small shifts in alpha-carbon positions in the model to give a minimized structure, suggesting that small changes in receptor conformation can affect the signaling state of the receptor.