title: Questioning of reported evidence for guanosine tetraphosphate synthesis in a ribosome system from mouse embryos.
abstract: In 1974, Irr, Kaulenas and Unsworth reported that ppGpp is synthesized by cytosolic ribosomes from mouse embryos and proposed a role for ppGpp in the process of differentiation. This proposal is being challenged because ribosomes of mouse embryos from various stages of development and of mouse embryoid bodies were completely inactive in ppGpp formation.
mesh_terms: D000818:Animals; D004622:Embryo, Mammalian / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D005865:Gestational Age; D006150:Guanine Nucleotides / Q000096:biosynthesis*; D006159:Guanosine Tetraphosphate / Q000096:biosynthesis*; D008566:Membranes / Q000378:metabolism; D051379:Mice; D012270:Ribosomes / Q000378:metabolism*
chemical_list: D006150:Guanine Nucleotides; D006159:Guanosine Tetraphosphate