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Biomedical subjects

B D Korant

Publications and source records attributed to B D Korant.

At least 55 records · Page 3Linked to original sources
PubMed1976

Inhibition by zinc of rhinovirus protein cleavage: interaction of zinc with capsid polypeptides.

Zinic ions rapidly inhibit virus production in HeLa cells infected with human rhinovirus type 1A and lead to the accumulation of human rhinovirus type 1A precursor polypeptides. The degree to which cleavage of these precursors is inhibited is directly dependent on the quantity of cell-associated zinc. Proteolysis resumes after the removal of zinc-containing medium, and the accumulated viral precursors are cleaved predominantly to stable virus polypeptides. The precursors stabilized at the lowest zinc levels are those that contain capsid protein sequences. Furthermore, added zinc is bound to human rhinovirus type 1A capsids and prevents them from forming crystals. Zinc-resistant mutants display antigenic alterations in coat proteins. These results suggest that zinc complexes with rhinovirus coat proteins and alters them so that they cannot function as substrates for proteases or as reactants in the assembly of the virus particles.

Capsid↗
PubMed1975

Electrophoretic analysis of capsid and non-capsid polypeptides of echovirus 12, and selective inhibtion of the formation of virus particles by actinomycin D.

Electrophoretic analysis of purified echovirus virus particles yielded four polypeptides of mol. wt. 37000, 30000, 25000 and 7600. The 75S empty capsids of echovirus 12 lack the 25000 and 7600 mol. wt. polypeptides, and possess polypeptides of 41000 mol. wt. A total of 14 virus-induced polypeptide species was found in the cytoplasm of infected cells. Actinomycin D reduced the synthesis of virus, virus RNA, and virus polypeptides and also reduced the proportion of virus particles to empty capsids in the virus yields.

Amino Acids↗
PubMed1974

Characterization of the large picornaviral polypeptides produced in the presence of zinc ion.

Zinc ion inhibits the posttranslational cleavages of human rhinovirus-1A, encephalomyocarditis virus, and poliovirus polypeptides. Each virus displayed a different susceptibility to zinc. However, in each case the cleavages of the capsid precursor and the cleavages analogous to the C --> D --> E conversion in encephalomyocarditis virus were most sensitive to zinc. Higher concentrations of zinc resulted in the buildup of even larger precursor polypeptides of a size between 106,000 and 214,000 daltons. The sizes of these polypeptides and the relative position of their gene loci on the viral RNA were determined. These data were used to place these polypeptides in the over-all scheme of viral protein processing.

Electrophoresis, Polyacrylamide Gel↗
PubMed1973

Cleavage of poliovirus-specific polypeptide aggregates.

Zonal electrophoresis resolves two aggregates of poliovirus type 2 cytoplasmic polypeptides. The more negatively charged aggregate contains mainly noncapsid viral-specific polypeptides (NCVP) 2 and x, whereas the other consists of the capsid polypeptides (VP) 0, 1, 2, and 3 (VP0, VP1, VP2, VP3). After treatment with sodium deoxycholate (DOC), the aggregates sediment at 5 to 6S. Their electrophoretic mobilities are unaffected by DOC or RNase. The capsid polypeptide aggregate is similar in mobility to virions but can be converted to a faster electrophoretic form, resembling empty capsids, by heating. If infected HeLa cells are allowed to synthesize poliovirus polypeptides in the presence of iodoacetamide, no capsid polypeptides are produced, but rather NCVP1a (the precursor to capsid polypeptides) is accumulated, along with NCVP2 and NCVPx. When analyzed by electrophoresis and centrifugation, uncleaved NCVP1a migrates with the NCVP2-x aggregate. NCVP1a can be cleaved to capsid-like polypeptides in vitro by using extracts of infected cells, but not uninfected cells, indicating either a virus-specified protease or a cellular enzyme activated during infection. After cleavage of NCVP1a by infected cell extracts, the capsid polypeptides which are produced dissociate from the NCVP2-x complex.

Acetamides↗
PubMed1972

Cleavage of viral precursor proteins in vivo and in vitro.

The use of protease inhibitors causes the accumulation of very large polypeptides (polyprotein) in tissue culture cells infected with either poliovirus or echovirus 12. The effectiveness of the inhibitor varies, depending on the cell line chosen. In infected monkey kidney cells, polyprotein is not cleaved when a chymotrypsin inhibitor is added, but in infected HeLa cells a trypsin inhibitor is most effective. Therefore, at least a part of the proteolytic activity is supplied by the host cell. Extracted viral polyprotein can be cleaved in vitro by trypsin or chymotrypsin. As estimated by migration in sodium dodecyl sulfate gels and antigenicity, chymotrypsin cleavage of the poliovirus polyprotein yields fragments which are similar to the in vivo product. The polyprotein is not in soluble form but is attached to a fast-sedimenting, membrane-bound structure. Proteolytic activities in cell extracts were assayed using polyprotein as substrate, and infected and uninfected extracts produced qualitatively dissimilar cleavages.

Animals↗
PubMed1972

Early interaction of rhinoviruses with host cells.

The rate of attachment of type 2 virions to suspensions of HeLa cells is much greater than that of type 14, but the number of receptor sites per cell is similar for each type. The receptor sites may be partly saturated with excess virions; attachment is greatly reduced after about 10(4) particles have been taken up per cell. A lack of saturation of type 14 receptors by excess type 2 indicates that their receptor sites are separate on the cell surface. Excess of type 2 blocks attachment of type 1A, however, and excess of type 14 blocks type 51. Attachment of the human rhinoviruses is temperature-dependent with a Q(10) of 2.7. The eclipse reaction is also temperature-dependent. At 34.5 C, the irreversible eclipse of cell-associated rhinovirus type 2 requires only a few minutes, whereas the rate of eclipse of cell-associated type 14 is considerably slower. The eclipse product of type 2 rhinovirus has been recovered from infected cells. It sediments at about 90% of the rate of the infective virions and is missing virus polypeptide 4 (the smallest of the capsid polypeptides). Upon being subjected to CsCl gradient centrifugation, virus polypeptide 2 is also lost but the product still contains ribonucleic acid and bands at about 1.45 g/cc.

Amino Acids↗