title: Isolation, structure, and antibacterial activity of philipimycin, a thiazolyl peptide discovered from Actinoplanes philippinensis MA7347.
abstract: Bacterial resistance to antibiotics, particularly to multiple drug resistant antibiotics, is becoming cause for significant concern. The only really viable course of action is to discover new antibiotics with novel mode of actions. Thiazolyl peptides are a class of natural products that are architecturally complex potent antibiotics but generally suffer from poor solubility and pharmaceutical properties. To discover new thiazolyl peptides potentially with better desired properties, we designed a highly specific assay with a pair of thiazomycin sensitive and resistant strains of Staphylococcus aureus, which led to the discovery of philipimycin, a new thiazolyl peptide glycoside. It was isolated along with an acid-catalyzed degradation product by bioassay-guided fractionation. Structure of both compounds was elucidated by extensive application of 2D NMR, 1D TOCSY, and HRESIFT-MS/MS. Both compounds showed strong antibacterial activities against gram-positive bacteria including MRSA and exhibited MIC values ranging from 0.015 to 1 microg/mL. Philipimycin was significantly more potent than the degradation product. Both compounds showed selective inhibition of protein synthesis, indicating that they targeted the ribosome. Philipimycin was effective in vivo in a mouse model of S. aureus infection exhibiting an ED50 value of 8.4 mg/kg. The docking studies of philipimycin suggested that a part of the molecule interacts with the ribosome and another part with Pro23, Pro22, and Pro26 of L11 protein, which helped in explaining the differential of activities between the sensitive and resistant strains. The design and execution of the bioassay, the isolation, structure, in vitro and in vivo antibacterial activity, and docking studies of philipimycin and its degradation product are described.
authors.affiliation: Merck Research Laboratories, Rahway, New Jersey 07065, USA.
authors.forename: Chaowei
authors.initials: C
authors.lastname: Zhang
authors.forename: James
authors.initials: J
authors.lastname: Occi
authors.forename: Prakash
authors.initials: P
authors.lastname: Masurekar
authors.forename: John F
authors.initials: JF
authors.lastname: Barrett
authors.forename: Deborah L
authors.initials: DL
authors.lastname: Zink
authors.forename: Scott
authors.initials: S
authors.lastname: Smith
authors.forename: Russell
authors.initials: R
authors.lastname: Onishi
authors.forename: Sookhee
authors.initials: S
authors.lastname: Ha
authors.forename: Oscar
authors.initials: O
authors.lastname: Salazar
authors.forename: Olga
authors.initials: O
authors.lastname: Genilloud
authors.forename: Angela
authors.initials: A
authors.lastname: Basilio
authors.forename: Francisca
authors.initials: F
authors.lastname: Vicente
authors.forename: Charles
authors.initials: C
authors.lastname: Gill
authors.forename: Emily J
authors.initials: EJ
authors.lastname: Hickey
authors.forename: Karen
authors.initials: K
authors.lastname: Dorso
authors.forename: Mary
authors.initials: M
authors.lastname: Motyl
authors.forename: Sheo B
authors.initials: SB
authors.lastname: Singh
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D001426:Bacterial Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D006027:Glycosides / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D008848:Micromonosporaceae / Q000737:chemistry*; D008958:Models, Molecular; D010456:Peptides, Cyclic / Q000494:pharmacology; D021241:Spectrometry, Mass, Electrospray Ionization; D013211:Staphylococcus aureus / Q000187:drug effects; D013844:Thiazoles / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D006027:Glycosides; D010456:Peptides, Cyclic; D013844:Thiazoles; C525268:thiazomycin