title: Polypeptide chain initiation in eukaryotes: mechanism of formation of initiation complex.
abstract: Artemia salina ribosomal subunits and highly purified reticulocyte initiation factors (IF) are used to study the mechanism of formation of the puromycin-sensitive initiation complex Met-tRNAi-80S ribosome-AUG. A complex with equimolar amounts of 40S subunit, GTP, and Met-tRNAi is formed at low Mg2+ concentration with a requirement for IF-MP (homogeneous) but not AUG or other factors. An 80S complex is formed only upon the further addition of AUG, IF-M2A, and IF-M2B, but not of either factor alone. This complex contains no GTP or GDP. A 40S complex, which cannot be converted to an 80S one, is formed when the nonhydrolyzable analog GMPPCP is substituted for GTP. IF-M2A has no effect on the formation of this complex, but IF-M2B enhances its formation.
mesh_terms: D000818:Animals; D003445:Crustacea / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D010442:Peptide Chain Initiation, Translational; D010448:Peptide Initiation Factors; D011691:Puromycin / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism*; D013698:Templates, Genetic
chemical_list: D010448:Peptide Initiation Factors; D011691:Puromycin; D006160:Guanosine Triphosphate; D012343:RNA, Transfer