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Biomedical subjects

B Korant

Publications and source records attributed to B Korant.

7 recordsLinked to original sources
PubMed1999

Inhibition of cysteine protease and growth of Staphylococcus aureus V8 and poliovirus by phosphorylated cystatin alpha conjugate of skin.

The inhibitory properties of phosphorylated cystatin alpha (P-cystatin alpha) and a conjugated protein of the P-cystatin alpha with filaggrin linker segment peptide (FLSP) against the growth of Staphylococcus bacteria and poliovirus were investigated. Both the P-cystatin alpha and the conjugated protein (P-cystatin alpha-FLSP conjugate) as a model for the cornified envelope of skin inhibited the cysteine protease activity of Staphylococcus aureus V8. The protease activity was inhibited by normal cornified envelope of newborn rat skin, which contains P-cystatin alpha, and P-cystatin alpha in cornified envelope of newborn rat skin also suppressed the growth of S. aureus V8. When P-cystatin alpha or P-cystatin alpha-FLSP conjugate was added to cultured HeLa cells infected with poliovirus, 50-70% of the cell-death due to poliovirus infection was prevented. The poliovirus 3C protease activity in the infected HeLa cells was inhibited by P-cystatin alpha or P-cystatin alpha-FLSP conjugate. As a result, the processing of viral capsid peptides was suppressed. These findings suggest that P-cystatin alpha and P-cystatin alpha-FLSP conjugate could play the role of the barrier against microorganism infections due to inhibition of their cysteine protease activities.

Amino Acid Sequence↗
PubMed1996

Improved cyclic urea inhibitors of the HIV-1 protease: synthesis, potency, resistance profile, human pharmacokinetics and X-ray crystal structure of DMP 450.

BACKGROUND: Effective HIV protease inhibitors must combine potency towards wild-type and mutant variants of HIV with oral bioavailability such that drug levels in relevant tissues continuously exceed that required for inhibition of virus replication. Computer-aided design led to the discovery of cyclic urea inhibitors of the HIV protease. We set out to improve the physical properties and oral bioavailability of these compounds. RESULTS: We have synthesized DMP 450 (bis-methanesulfonic acid salt), a water-soluble cyclic urea compound and a potent inhibitor of HIV replication in cell culture that also inhibits variants of HIV with single amino acid substitutions in the protease. DMP 450 is highly selective for HIV protease, consistent with displacement of the retrovirus-specific structural water molecule. Single doses of 10 mg kg-1 DMP 450 result in plasma levels in man in excess of that required to inhibit wild-type and several mutant HIVs. A plasmid-based, in vivo assay model suggests that maintenance of plasma levels of DMP 450 near the antiviral IC90 suppresses HIV protease activity in the animal. We did identify mutants that are resistant to DMP 450, however; multiple mutations within the protease gene caused a significant reduction in the antiviral response. CONCLUSIONS: DMP 450 is a significant advance within the cyclic urea class of HIV protease inhibitors due to its exceptional oral bioavailability. The data presented here suggest that an optimal cyclic urea will provide clinical benefit in treating AIDS if it combines favorable pharmacokinetics with potent activity against not only single mutants of HIV, but also multiply-mutant variants.

Administration, Oral↗
PubMed1988

Interactions between a viral protease and cystatins.

The interactions of two cystatins with a viral cysteine protease were studied using several types of assays. Complex formation between the protease and inhibitor was directly demonstrated using a gel retardation assay. It was also shown that the formation of enzyme inhibitor complexes could occur after first binding either the enzyme or the inhibitor to filter paper, and ultimately decorating the complex with antibody and radio-labelled protein A or by preparing one of the protein ligands with an internal radiolabel. The procedure can be adapted to provide a method for screening expression libraries for protease or inhibitor genes. The inhibition of a cysteine protease by a cystatin was shown not to directly involve binding to the active site thiol of the enzyme, but rather to be the result of a steric block in the active site region which prevents large affinity labels and protein substrates from reaching the active site.

Animals↗
PubMed1984

Transcriptional induction of two genes in human cells by beta interferon.

The binding of interferons to distinct cell surface receptors leads to the induction of synthesis of several unique polypeptides and their corresponding mRNAs (1-6). We have isolated two cDNAs that are complementary to nuclear RNA whose synthesis is induced from undetectable levels to maximal rates of transcription within 30-60 min after the addition of beta interferon to human fibroblasts or to HeLa cells. These results prove that a single polypeptide can, by binding to a specific plasma membrane receptor, promptly activate the transcription of a defined set of genes.

DNA↗
PubMed1979

Virus-specified protease in poliovirus-infected HeLa cells.

Previous studies have shown that primary cleavages in nascent picornavirus precursors are accomplished by cellular proteases. This study has characterized the enzyme in infected cells that produces the capsid polypeptides by secondary cleavages of viral precursors. The kinetics of the production of protease activity correlate with the time course of virus protein synthesis, and the new enzyme has characteristic pH and temperature optima. Guanidine and cycloheximide, which are inhibitors of virus RNA and protein synthesis, prevent production of the protease. As determined by introduction of amino acid analogs into the protease or inhibition by a leucyl chloromethyl ketone, the enzyme is synthesized at a time of infection when host cell proteins are not produced, and the enzyme copurified with a 40,000-dalton virus polypeptide present in the cytoplasm of infected cells. Wild-type levels of protease activity are produced by viral mutants that are defective in coat protein synthesis. The conclusion is that a non-structural poliovirus gene product participates in protein cleavages that produce the viral coat proteins.

HeLa Cells↗