Isolation and characterization of an organ specific ribonucleoprotein from goat brain

Abstract

An organ specific protein (NP) has been isolated from the goat brain by salt fractionation and preparative polyacrylamide gel electrophoresis. The antiserum against this protein gave immunological cross reaction with the brain extracts of a wide variety of animals but did not react with extracts of liver, lung, kidney, spleen, heart and blood. Similar proteins have also been found to be present in monkey brain and human astrocytomas in culture. Evidence is presented to show that it is a ribonucleoprotein. This is based on the following observations: (1) its absorption characteristics before and after RNase treatment, (2) chemical analysis showing the presence of ribose, purines and pyrimidines, (3) incorporation of radioactive uridine and lysine in monkey brain and in human astrocytomas in culture into a protein band having electrophoretic mobility and immunological characteristics analogous to NP protein. The molecular weight of the NP protein has been found to be 25,120 Daltons, while the residual moiety after treatment with RNase has a molecular weight of 19,060. The RNA content of NP protein in four separate preparations was 20.65% (±0.55 S.D.) as determined by the orcinol colour reaction and 23.85% (±0.88 S.D.) gauged by the ratio of extinctions at 260 and 280 nm. The base composition of RNA has also been determined. The nature of association of the RNA moiety with the protein is not known. The two are, however, not dissociable by SDS and high pH excluding the possibility of aminoacyl linkage and nonspecific adsorption.