Bcel-2 family proteins (Bcl-x(L), Bcl-2, Mel-1 etc.) are key regulators of some life processes, including apoptosis and autophagy. They are currently considered as promising targets for developing new anti-tumor therapies. In our study, the human Bcl-2/Bcl-x(L) chimeric gene and the human/mouse Mel-1 chimeric gene were designed and cloned, and the prokaryotic expression vectors for expressing glutathione S-transferase (GST) fusion proteins and histidine tag fusion proteins were constructed respectively. These two proteins as well as the GST-Bcl-x(L) fusion protein were all successfully expressed in E. coli and subsequently purified. In addition, we measured the binding of these Bcl-2 family proteins to the Bid BH3 peptide by fluorescence polarization-based assay. The dissociation constants (Kd) obtained by us were in general agreement with the data reported in literature. The Kd values of all three proteins with or without the GST tag were almost identical. All these results validate the biological functions of these Bcl-2 family proteins obtained by us. These proteins can be used in the experimental screening of small-molecule regulators of Bcl-2 family proteins in vitro.
Escherichia coli ; genetics ; metabolism ; Fluorescence Polarization ; methods ; Glutathione Transferase ; biosynthesis ; genetics ; Humans ; Myeloid Cell Leukemia Sequence 1 Protein ; Proto-Oncogene Proteins c-bcl-2 ; biosynthesis ; genetics ; isolation & purification ; Recombinant Fusion Proteins ; biosynthesis ; genetics ; isolation & purification ; bcl-X Protein ; biosynthesis ; genetics ; isolation & purification

OBJECTIVETo evaluate the effectiveness of small interfering RNA (siRNA) on inhibiting severe acute respiratory syndrome (SARS)-associated coronavirus replication, and to lay bases for the future clinical application of siRNA for the treatment of viral infectious diseases.

METHODSVero-E6 cells was transfected with siRNA before SARS virus infection, and the effectiveness of siRNA interference was evaluated by observing the cytopathic effect (CPE) on Vero-E6 cells.

RESULTSFive pairs of siRNA showed ability to reduce CPE dose dependently, and two of them had the best effect.

CONCLUSIONsiRNA may be effective in inhibiting SARS-associated coronavirus replication.

Animals ; Cercopithecus aethiops ; RNA, Small Interfering ; pharmacology ; SARS Virus ; drug effects ; Transfection ; Vero Cells ; Virus Replication ; drug effects

Polyoxin is a group of structurally-related peptidyl nucleoside antibiotics bearing C-5 modifications on the nucleoside skeleton. Although the structural diversity and bioactivity preference of polyoxin are, to some extent, affected by such modifications, the biosynthetic logic for their occurence remains obscure. Here we report the identification of PolB in polyoxin pathway as an unusual UMP C-5 methylase with thymidylate synthase activity which is responsible for the C-5 methylation of the nucleoside skeleton. To probe its molecular mechanism, we determined the crystal structures of PolB alone and in complexes with 5-Br UMP and 5-Br dUMP at 2.15 Å, 1.76 Å and 2.28 Å resolutions, respectively. Loop 1 (residues 117-131), Loop 2 (residues 192-201) and the substrate recognition peptide (residues 94-102) of PolB exhibit considerable conformational flexibility and adopt distinct structures upon binding to different substrate analogs. Consistent with the structural findings, a PolB homolog that harbors an identical function from Streptomyces viridochromogenes DSM 40736 was identified. The discovery of UMP C5-methylase opens the way to rational pathway engineering for polyoxin component optimization, and will also enrich the toolbox for natural nucleotide chemistry.
Bacterial Proteins ; chemistry ; Crystallography, X-Ray ; Methyltransferases ; chemistry ; Protein Domains ; Protein Structure, Secondary ; Pyrimidine Nucleosides ; biosynthesis ; Streptomyces ; enzymology