A single-stranded nucleic acid binding sequence common to the heterogeneous nuclear ribonucleoparticle protein A1 and murine recombinant virus gp70.

We have used an antisynthetic peptide antiserum to a murine recombinant virus gp70 to probe normal mouse tissues for immunologically related proteins. In addition to cognate gp70s, this antiserum reacts with the heterogeneous nuclear ribonucleoparticle protein A1 by virtue of a 5-amino acid epitope, PRNQG. Further structural similarity is evident both 5' and 3' of this epitope. Since the function of the heterogeneous nuclear ribonucleoprotein particles in the cell is to aid in the stabilization and processing of newly synthesized RNA, we have investigated whether this retroviral sequence exhibits any nucleic acid-binding properties by the same criteria established for the identification of heterogeneous nuclear ribonucleoprotein particles. Analysis of the peptide in a poly(eA) binding assay shows this retroviral sequence to bind with high affinity to single-stranded nucleic acid. This binding occurs in a salt-sensitive manner characteristic of single-stranded nucleic acid-binding proteins. Flanking peptides not containing this sequence generated from either the A1 or gp70 show no ability to bind single-stranded nucleic acids by this assay.     

p10, a low molecular weight single-stranded nucleic acid binding protein of murine leukemia retroviruses, shows stacking interactions of its single tryptophan residue with nucleotide bases

Room temperature fluorescence and low-temperature phosphorescence studies of the association of p10, a basic low molecular weight single-stranded DNA binding protein isolated from murine leukemia viruses, point to the involvement of its single tryptophan residue in a close-range interaction with single-stranded polynucleotides. Optically detected triplet-state magnetic resonance (ODMR) techniques applied to the complex of p10 protein with the heavy atom derivatized polynucleotide poly(5-HgU) demonstrate the occurrence of stacking interactions of Trp35 with nucleic acid bases, thus agreeing with earlier reports that this residue is involved in the binding process [Karpel, R. L., Henderson, L. E., & Oroszlan, S. (1987) J. Biol. Chem. 262, 4961-4967].