Separation of proteins of nuclear ribonucleoprotein particles by high-performance liquid chromatography

High-performance liquid chromatography (h.p.l.c.) is used to fractionate the proteins of the 30–40 S nuclear ribonucleoprotein particles. The major core proteins of the particles are eluted from a SynChropak AX-300 anion-exchange column before the more acidic higher-molecular-weight minor particle proteins. Each of the three major core proteins which can be separated from the other particle proteins by preparative polyacrylamide gel electrophoresis are eluted from the SynChropak AX-300 column as one peak. Isoelectric focusing separates each of these three apparently homogeneous peaks into a series of charge isomers ranging in isoelectric pH (pI) from 5.5 to 9.0. The core proteins of the ribonucleoprotein particles have a strong affinity to each other and form aggregates. The elution of each of the charge isomers of the three major proteins in one peak and their elution from an anion exchanger before the elution of the more acidic higher-molecular-weight minor proteins of the nuclear ribonucleoprotein particles is explained by the formation of these aggregates. The separation of the total proteins of the nuclear ribonucleoprotein particles by h.p.l.c. is similar to the separation which can be obtained by preparative electrophoresis but the l.c. technique is simpler, substantially quicker, and adaptable to large-scale preparation.