ABSTRACT
The conserved, ATP-dependent bacterial DnaK chaperones process client substrates with the aid of the co-chaperones DnaJ and GrpE. However, in the absence of structural information, how these proteins communicate with each other cannot be fully delineated. For the study reported here, we solved the crystal structure of a full-length Geobacillus kaustophilus HTA426 GrpE homodimer in complex with a nearly full-length G. kaustophilus HTA426 DnaK that contains the interdomain linker (acting as a pseudo-substrate), and the N-terminal nucleotide-binding and C-terminal substrate-binding domains at 4.1-Å resolution. Each complex contains two DnaKs and two GrpEs, which is a stoichiometry that has not been found before. The long N-terminal GrpE α-helices stabilize the linker of DnaK in the complex. Furthermore, interactions between the DnaK substrate-binding domain and the N-terminal disordered region of GrpE may accelerate substrate release from DnaK. These findings provide molecular mechanisms for substrate binding, processing, and release during the Hsp70 chaperone cycle.
Subject(s)
Bacterial Proteins/chemistry , Geobacillus/chemistry , Heat-Shock Proteins/chemistry , Protein Multimerization , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , Binding Sites , Crystallography, X-Ray , Geobacillus/genetics , Geobacillus/metabolism , Heat-Shock Proteins/genetics , Heat-Shock Proteins/metabolism , Protein Structure, Quaternary , Protein Structure, SecondaryABSTRACT
Five new sesquiterpene lactones, spicatolides D-H (1-5), along with four known compounds, pitocarphin D (6), 8 alpha-acetoxy-10 alpha-hydroxy-13-O-methylhirsutinolide (7), spicatolide A (8), and 13-O-methylvernojalcanolide 8-O-acetate (9), were isolated from an ethyl acetate extract of the aerial parts of Pseudoelephantopus spicatus. The structures of the new compounds were elucidated on the basis of spectroscopic data interpretation. All of the compounds isolated were evaluated for their cytotoxic effects against five human cancer cell lines. Compounds 1, 3, and 4 showed cytotoxicity (IC50 < 5 micro g/mL) against the Hep3B and MCF-7 cancer cell lines.
Subject(s)
Antineoplastic Agents, Phytogenic/isolation & purification , Antineoplastic Agents, Phytogenic/pharmacology , Asteraceae/chemistry , Lactones/isolation & purification , Lactones/pharmacology , Plants, Medicinal/chemistry , Sesquiterpenes/isolation & purification , Sesquiterpenes/pharmacology , Antineoplastic Agents, Phytogenic/chemistry , Drug Screening Assays, Antitumor , Humans , Lactones/chemistry , Molecular Conformation , Molecular Structure , Sesquiterpenes/chemistry , TaiwanABSTRACT
Fifteen new withanolides (1-8, 11-17) and two known withanolides, withanolide D (9) and 17alpha-hydroxywithanolide D (10), were isolated from the stems, roots, and leaves of Tubocapsicum anomalum using bioassay-directed fractionation. The structures were determined by spectroscopic and chemical methods, and the absolute configurations were established by CD analysis and by the Mosher ester method. The structure of 1 and 3 were further confirmed by X-ray crystallographic analysis. Compounds 1, 4-6, 8-10, and 13 showed significant cytotoxic activity against Hep G2, Hep 3B, A-549, MDA-MB-231, MCF-7, and MRC-5 cell lines.
Subject(s)
Antineoplastic Agents, Phytogenic , Ergosterol/analogs & derivatives , Plants, Medicinal/chemistry , Solanaceae/chemistry , Antineoplastic Agents, Phytogenic/chemistry , Antineoplastic Agents, Phytogenic/isolation & purification , Antineoplastic Agents, Phytogenic/pharmacology , Crystallography, X-Ray , Drug Screening Assays, Antitumor , Ergosterol/chemistry , Ergosterol/isolation & purification , Ergosterol/pharmacology , Humans , Molecular Conformation , Molecular Structure , Plant Leaves/chemistry , Plant Roots/chemistry , Plant Stems/chemistry , Taiwan , WithanolidesABSTRACT
A new cyclic peptide, longicalycinin A (1), and six known compounds, vaccaroside A, dianoside A, dianoside G, 3-(4-hydroxy-3-methoxy-phenyl)propionic acid methyl ester, p-hydroxybenzoic acid, and p-hydroxybenzaldehyde were isolated from the MeOH extract of Dianthus superbus var. longicalycinus. The amino acid sequences of 1 was elucidated as cyclo(Gly(1)-Phe(2)-Tyr(3)-Pro(4)-Phe(5)-) on the basis of ESI tandem mass fragmentation analysis, chemical evidence, and extensive 2D NMR methods. Furthermore, compound 1 showed cytotoxicity to Hep G2 cancer cell line.
Subject(s)
Antineoplastic Agents, Phytogenic/chemistry , Antineoplastic Agents, Phytogenic/toxicity , Dianthus/chemistry , Peptides, Cyclic/chemistry , Peptides, Cyclic/toxicity , Amino Acid Sequence , Animals , Antineoplastic Agents, Phytogenic/isolation & purification , Cell Line, Tumor , Drug Screening Assays, Antitumor , Humans , Peptides, Cyclic/isolation & purificationABSTRACT
Four new cyclic peptides, dianthins C-F (1-4), and a new dianthramide, 4-methoxydianthramide B (5), were isolated from the MeOH extract of the traditional Chinese medicinal plant Dianthus superbus. The sequences of cyclic peptides 1-4 were elucidated as cyclo(Gly(1)-Pro(2)-Phe(3)-Tyr(4)-Val(5)-Ile(6)-), cyclo(Gly(1)-Ser(2)-Leu(3)-Pro(4)-Pro(5)-Ile(6)-Phe(7)-), cyclo(Gly(1)-Pro(2)-Ile(3)-Ser(4)-Phe(5)-Val(6)-), and cyclo(Gly(1)-Pro(2)-Phe(3)-Val(4)-Phe(5)-) on the basis of ESI tandem mass fragmentation analysis, chemical evidence, and extensive 2D NMR methods. The conformation of compound 1 was established as an alpha-helix by CD analysis. Furthermore, compounds 3 and 5 showed cytotoxicities toward the Hep G2 cancer cell line with IC(50) values of 2.37 and 4.08, respectively.
