title: A switch-on mechanism to activate maize ribosome-inactivating protein for targeting HIV-infected cells.
abstract: Maize ribosome-inactivating protein (RIP) is a plant toxin that inactivates eukaryotic ribosomes by depurinating a specific adenine residue at the α-sarcin/ricin loop of 28S rRNA. Maize RIP is first produced as a proenzyme with a 25-amino acid internal inactivation region on the protein surface. During germination, proteolytic removal of this internal inactivation region generates the active heterodimeric maize RIP with full N-glycosidase activity. This naturally occurring switch-on mechanism provides an opportunity for targeting the cytotoxin to pathogen-infected cells. Here, we report the addition of HIV-1 protease recognition sequences to the internal inactivation region and the activation of the maize RIP variants by HIV-1 protease in vitro and in HIV-infected cells. Among the variants generated, two were cleaved efficiently by HIV-1 protease. The HIV-1 protease-activated variants showed enhanced N-glycosidase activity in vivo as compared to their un-activated counterparts. They also possessed potent inhibitory effect on p24 antigen production in human T cells infected by two HIV-1 strains. This switch-on strategy for activating the enzymatic activity of maize RIP in target cells provides a platform for combating pathogens with a specific protease.
authors.affiliation: Department of Biochemistry and Centre for Protein Science and Crystallography, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, China.
authors.forename: Sue Ka-Yee
authors.initials: SK
authors.lastname: Law
authors.forename: Rui-Rui
authors.initials: RR
authors.lastname: Wang
authors.forename: Amanda Nga-Sze
authors.initials: AN
authors.lastname: Mak
authors.forename: Kam-Bo
authors.initials: KB
authors.lastname: Wong
authors.forename: Yong-Tang
authors.initials: YT
authors.lastname: Zheng
authors.forename: Pang-Chui
authors.initials: PC
authors.lastname: Shaw
mesh_terms: D000595:Amino Acid Sequence; D019380:Anti-HIV Agents / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D002460:Cell Line; D004789:Enzyme Activation; D016333:HIV Protease / Q000378:metabolism; D015497:HIV-1 / Q000502:physiology; D006801:Humans; D008969:Molecular Sequence Data; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D054788:Ribosome Inactivating Proteins / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology*; D013601:T-Lymphocytes / Q000821:virology; D003313:Zea mays / Q000201:enzymology; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000235:genetics
chemical_list: D019380:Anti-HIV Agents; D011993:Recombinant Fusion Proteins; D054322:tat Gene Products, Human Immunodeficiency Virus; D054788:Ribosome Inactivating Proteins; D016333:HIV Protease; C514803:p16 protease, Human immunodeficiency virus 1