A brain protein unique to the olfactory bulb.

Soluble extracts from several regions of the mouse brain manifested regionally specific protein band patterns on polyacrylamide gel electrophoresis. In particular, one protein band appeared to occur uniquely in the olfactory bulb extracts where it was a quantitatively significant constituent of the soluble protein extract. This protein was purified to homogeneity by ammonium sulfate precipitation, DEAE-cellulose column chromatography, and polyacrylamide gel electrophoresis. The purified protein has a minimum molecular weight of about 20,000 by gel electrophoresis in the presence of sodium dodecyl sulfate. Precipitating antiserum prepared against this protein reacted only with the purified protein or with extracts of olfactory bulb, and not with extracts of other mouse tissues or brain regions. Quantitative immunoprecipitation assays indicate that this specific protein represents 1% of the total soluble protein in the mouse olfactory bulb. Soluble extracts of olfactory bulbs from several rodent species gave reactions of identity by agar gel diffusion with the antiserum to the mouse protein. It is suggested that this protein is an example of selective genetic expression within the central nervous system.