[Physico-chemical characteristics of highly purified ceruloplasmin mRNA from rat liver].

Highly purified preparations of mRNA coding for ceruloplasmin (CP) ere isolated from rat liver polyribosomes using indirect immunoprecipitation of CP polysomes and poly(U)-sepharose chromatography of polysomal RNA. The homogeneity of CP mRNA was as high as 86--90%. The molecular weight of CP mRNA is 1.3 . 10(6) daltons which is in excess when compared to the minimal size of mRNA necessary to code for CP precursor (about 700 amino acid residues). The base composition of CP mRNA is of AU-type. The experiments on end-labeling with [3H]borohydride after periodate oxidation whowed that CP mRNA contains 3'-terminal poly(A). Poly(U)-sepharose chromatography with stepwise temperature elution revealed length heterogeneity of poly(A) consisting of particular, different thermal subfractions of CP mRNA contain poly(A) consisting of 38, 90 and 165 adenylate residue. 5'-end of CP mRNA is block with inverted 7-methylguanosine (m7G) which is reducible with [3H]borohydride after periodate oxidation. This m7G residue is a component of RNAse- and alkali-resistant oligonucleotide, which structure according to net charge value and its shifts after various enzymatic treatments, is m7G5'ppp5'XmpAp.