Complete amino acid sequence of pyrazine‐binding protein from cow nasal mucosa

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Abstract
The sequence is reported of the pyrazine-binding protein from cow olfactory/respiratory mucosa. The protein consists of 159 amino acids and clearly belongs to the retinol-binding protein family. It is most closely related to the urinary proteins from mice and rats and to the odour-binding protein from rat nasal epithelium. It is unique however, in that only one of the otherwise conserved features of the family is still present – namely a single tryptophan. Most surprisingly the protein contains no cysteine and, therefore, does not rely for its structural stability on the disulphide bond(s) present in other members of this group. A model for the protein has been constructed based on the co-ordinates of β-lactoglobulin. From this, it is possible to identify residues which may line the binding site. The impression gained is of a much larger pocket than occurs with retinol-binding protein or β-lactoglobulin. The character of the binding pocket remains essentially hydrophobic but with a significant reduction in its aromatic content and an increase in H-bonding side chains.