Structural and Immunological Properties of Neuron Specific Protein (Nsp) From Rat, Cat and Human Brain: Comparison to Bovine 14‐3‐2

Neuron specific protein (NSP) has been isolated from cat (NSP‐C) and human (NSP‐H) brain utilizing the purification procedure described for rat brain 14‐3‐2 (M arangos et al. , 1975a,b,c), a protein which is now designated NSP‐R. The protein as isolated from cat and human brain has a molecular weight of approx 80,000 as determined by sedimentation equilibrium. Sedimentation studies done in the presence of 6mg‐HCl and 0.2%β mercaptoethanol yields a protomer M.W. of approx 40,000 for both preparations establishing the dimeric nature of each. The subunits appear identical in each case since one band is observed upon electrophoresis of either preparation in the presence of 8 M‐urea. NSP‐C and NSP‐H have identical isoelectric points of 4.7 making them slightly more acidic than NSP‐R (pi = 5.0). Comparison of NSP‐C and NSP‐H with NSP‐R and bovine 14‐3‐2 by electrophoretic and immunological criteria revealed that the cat, human and bovine proteins were very similar. NSP‐R can be distinguished from the other three preparations electrophoretically and immunologically. The protomer unit of NSP‐R differs in amino acid composition from that of the cat, human or bovine proteins since the former can be completely resolved from any of the latter three preparations on 8 M‐urea polyacrylamide gels. The data indicate that NSP and bovine 14‐3‐2 are probably homologous proteins, and establish the general structural properties of NSP.