title: The action mode of the ribosome-inactivating protein alpha-sarcin.
abstract: Based on the tertiary structure of the ribosome-inactivating protein alpha-sarcin, domains that are responsible for hydrolyzing ribosomes and naked RNA have been dissected. In this study, we found that the head-to-tail interaction between the first amino beta-strand and the last carboxyl beta-strand is not involved in catalyzing the hydrolysis of ribosomes or ribonucleic acids. Instead, a four-strand pleated beta-sheet is indispensable for catalyzing both substrates, suggesting that alpha-sarcin and ribonuclease T1 (RNase T1) share a similar catalytic center. The integrity of an amino beta-hairpin and that of the loop L3 in alpha-sarcin are crucial for recognizing and hydrolyzing ribosomes in vitro and in vivo. However, a mutant protein without the beta-hairpin structure, or with a disrupted loop L3, is still capable of digesting ribonucleic acids. The functional involvement of the beta-hairpin and the loop L3 in the sarcin stem/loop RNA of ribosomes is demonstrated by a docking model, suggesting that the two structures are in essence naturally designed to distinguish ribosome-inactivating proteins from RNase T1 to inactivate ribosomes.
authors.affiliation: Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan, ROC.
authors.forename: L
authors.initials: L
authors.lastname: Hwu
authors.forename: K
authors.initials: K
authors.lastname: Huang
authors.forename: D
authors.initials: D
authors.lastname: Chen
authors.forename: A
authors.initials: A
authors.lastname: Lin
mesh_terms: D000818:Animals; D004722:Endoribonucleases / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*; D004926:Escherichia coli / Q000235:genetics; D005656:Fungal Proteins; D006868:Hydrolysis; D007544:Isopropyl Thiogalactoside / Q000494:pharmacology; D008958:Models, Molecular; D009154:Mutation; D011487:Protein Conformation; D012313:RNA / Q000378:metabolism; D011817:Rabbits; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012156:Reticulocytes / Q000378:metabolism; D012260:Ribonucleases / Q000378:metabolism; D012270:Ribosomes / Q000502:physiology
chemical_list: D005656:Fungal Proteins; D011994:Recombinant Proteins; C014801:alpha-sarcin; D007544:Isopropyl Thiogalactoside; D012313:RNA; D004722:Endoribonucleases; D012260:Ribonucleases