The 38,000-Mr poly(A)-binding protein of non-polysomal messenger ribonucleoproteins of cryptobiotic gastrulae of Artemia salina.

The 38,000-Mr poly(A)-binding protein has been purified to near homogeneity from non-polysomal messenger ribonucleoprotein of Artemia salina [Slegers, H., De Herdt, E., and Kondo, M. (1981) Eur. J. Biochem. 117, 111-120]. The protein consists of approximately 357 amino acids and is characterized by a high glycine content of 22.5% and the presence of dimethylarginine. From polynucleotide-protein binding experiments a stoichiometry of 9-11 adenylate and 10-12 uridylate residues per protein molecule is calculated. The polypeptide is devoid of poly(A) polymerase and RNase activities. The poly(A)-binding protein and the helix-destabilizing protein HD40 [Marvil, D. K., Nowak, L., and Szer, W. (1980) J. Biol. Chem. 255, 6466-6472] have the same mobility in polyacrylamide/dodecylsulphate gel electrophoresis and exhibit a comparable amino acid composition and protein-polynucleotide stoichiometry. Based on the length of poly(A) sequences of mRNA and from protein-poly(A) binding experiments, a repetitive binding of the 38,000-Mr protein on the poly(A) sequence is demonstrated. The 38,000-Mr protein of cytoplasmic and membrane-bound non-polysomal messenger ribonucleoproteins is also compared.