Properties of a 110000 molecular weight protein in rat liver hnRNP particles.

Particles carrying heterogeneous nuclear RNA (30--40 S-particles) were isolated from rat liver nuclei and the particle proteins separated by sodium dodecylsulfate gel electrophoresis. Some properties of a 110000 molecular weight component (P 110/103) were studied in detail: (i) P 110/103 was labeled to a 4-5 times higher specific activity than the major particle proteins in the presence of [14C]-amino acids in vivo. (ii) In nuclei incubated with [3H]- or [32P]-nicotinamide adenine dinucleotide P 110/103 was labeled presumably by ADP-ribosylation. (iii) A protein with the same molecular weight as P 110/103 and isolated from the nuclear extract by affinity chromatography was phosphorylated in vitro.