Cotranslational folding of globin.
Globin synthesis in a wheat germ cell-free translation system was performed in the presence of [3H]hemin and [35S]methionine to determine the minimal length of the nascent ribosome-bound globin chain capable of heme binding. Nascent polypeptides of predetermined size were synthesized on ribosomes by translation of truncated mRNA molecules. Analysis with the use of sucrose gradient centrifugation and puromycin reaction revealed that the ribosome-bound N-terminal alpha-globin fragments of 140, 100, and 86 amino acid residues are capable of an efficient heme binding, whereas those of 75, 65, and 34 amino acid residues display a significantly weaker, or just nonspecific, affinity to heme. This indicates that the ribosome-bound nascent chain of 86 amino acid residues has already acquired a spatial structure that allows its interaction with the heme group or that heme attachment promotes the formation of the proper tertiary structure in the ribosome-bound nascent peptide. In any case the cotranslational folding of globin is suggested.
Komar
A A
AA
Department of Molecular Biology, Faculty of Biology, Moscow State University, 119899 Moscow, Russia.
Kommer
A
A
Krasheninnikov
I A
IA
Spirin
A S
AS
D000818:Animals; D002474:Cell-Free System; D003001:Cloning, Molecular; D017931:DNA Primers; D005914:Globins / Q000096:biosynthesis* / Q000737:chemistry*; D006427:Hemin / Q000378:metabolism; D008715:Methionine / Q000378:metabolism; D008961:Models, Structural; D009838:Oligodeoxyribonucleotides; D016133:Polymerase Chain Reaction; D014176:Protein Biosynthesis; D011487:Protein Conformation; D017510:Protein Folding; D012333:RNA, Messenger / Q000378:metabolism; D011817:Rabbits; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D013462:Sulfur Radioisotopes; D014158:Transcription, Genetic; D014908:Triticum; D014316:Tritium
D017931:DNA Primers; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D011994:Recombinant Proteins; D013462:Sulfur Radioisotopes; D014316:Tritium; D006427:Hemin; D005914:Globins; D008715:Methionine