Identification and properties of the 38000‐M, poly(A)‐binding protein of non‐polysomal messenger ribonucleoproteins of cryptobiotic gastrulae of Artemia salina

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Abstract
The Mr‐38000 poly(A)‐binding protein interacts with synthetic and natural RNA. A sequence‐independent stoichiometry of one protein per 8–12 nucleotides is measured by filter binding and sucrose gradient centrifugation. Specificity for the poly(A) sequence is demonstrated from poly(A)/RNA mixing experiments. The poly(A)‐binding protein has been identified as the helix‐destabilizing protein HD40 [Marvil, D. K., Nowak, L. and Szer, W. (1980) J. Biol. Chem. 255, 6466–6472] and is characterized by the existence of at least seven ionic species with a pl ranging from 9.2 to 6.6. Acidic ionic species are generated by phosphorylation with mRNP‐associated protein kinase. Different ionic species are present on free mRNP and ribosomes‐mRNP preinitiation complexes. The poly(A)‐binding protein affects mRNA translation and (A)4 polyadenylation. The multifunctionality of the protein is discussed.