Isolation and partial purification of catfish pancreatic islet messenger RNA.
Poly(a)-rich mRNA has been isolated from catfish pancreatic islet total nucleic acid. Cell-free translation of the mRNA by wheat germ extracts yielded a protein of 11 000-12 000 molecular weight, estimated by sodium dodecyl sulfate-urea polyacrylamide gel electrophoresis. This peptide is larger than catfish proinsulin, but contains tryptic peptides of proinsulin. Its synthesis comprises up to 23% of the cell-free product, depending on the conditions of cell-free synthesis. Synthesis is inhibited by 7-methylguanosine 5'-monophosphate suggesting the presence of a 7-methylguanosine cap on the 5' end of catfish proinsulin mRNA. Sucrose gradient centrifugation of the islet poly(A)-rich mRNA yielded 8S and 12S peaks. These fractions were translated with wheat germ extracts and it was determined that over 60% of the islet mRNA-dependent protein from the 8S fraction was preproinsulin. The 8S mRNA fraction was electrophoresed on 3% agarose-6 M urea gels and demonstrated to be several bands, ranging from 100 000-200 000 molecular weight.
D000818:Animals; D005399:Fishes; D007515:Islets of Langerhans / Q000378:metabolism*; D008970:Molecular Weight; D010446:Peptide Fragments / Q000032:analysis; D010944:Plants / Q000378:metabolism; D011061:Poly A / Q000032:analysis; D011384:Proinsulin / Q000096:biosynthesis; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000302:isolation & purification* / Q000378:metabolism; D014908:Triticum / Q000378:metabolism
D010446:Peptide Fragments; D012333:RNA, Messenger; D011061:Poly A; D011384:Proinsulin