title: Independency of anti-HIV-1 activity from ribosome-inactivating activity of trichosanthin.
abstract: Trichosanthin (TCS) is a type I ribosome-inactivating (RI) protein possessing multiple biological and pharmacological activities. Its major action is inhibition of human immunodeficiency virus (HIV) replication but the mechanism is still elusive. All evidences showed that this action is related to its RI activity. Previous studies found that TCS mutants with reduced RI activity simultaneously lost some anti-HIV activity. In this study, an exception was demonstrated by two TCS mutants retaining almost all RI activity but were devoid of anti-HIV-1 activity. Five mutants were constructed by using site-directed mutagenesis with either deletion or addition of amino acids to the C-terminal sequence. Results showed that the RI activity of mutants with C-terminal deletion mutants (TCS(C2), TCS(C4), and TCS(C14)) decreased by 1.2-3.3-fold with parallel downshifting of its anti-HIV-1 activity (1.4-4.8-fold). Another two mutants, TCS(C19aa) and TCS(KDEL) having 19 amino acid extension and a KDEL signal sequence added to the C-terminal sequence, retained all RI activity but subsequently lost most of the anti-HIV-1 activity. These findings suggested that ribosome inactivation alone might not be adequate to explain the anti-HIV action of TCS.
authors.affiliation: Laboratory of Molecular Immunopharmacology, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China.
authors.forename: Jian-Hua
authors.initials: JH
authors.lastname: Wang
authors.forename: Hui-Ling
authors.initials: HL
authors.lastname: Nie
authors.forename: Hai
authors.initials: H
authors.lastname: Huang
authors.forename: Siu-Cheung
authors.initials: SC
authors.lastname: Tam
authors.forename: Yong-Tang
authors.initials: YT
authors.lastname: Zheng
mesh_terms: D000595:Amino Acid Sequence; D019380:Anti-HIV Agents / Q000737:chemistry / Q000494:pharmacology*; D002460:Cell Line; D004797:Enzyme-Linked Immunosorbent Assay; D015497:HIV-1 / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D012270:Ribosomes / Q000187:drug effects*; D015978:Trichosanthin / Q000737:chemistry / Q000494:pharmacology*; D014779:Virus Replication / Q000187:drug effects
chemical_list: D019380:Anti-HIV Agents; D015978:Trichosanthin