Roberto A. Collins

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The ribosome inactivating proteins (RIPs) are a group of proteins that are able to inactivate eukaryotic protein synthesis by attacking the 28S ribosomal RNA. Recent studies have shown that some RIPs possess strong anti-human immunodeficiency virus (HIV) activity. In this study, several common plant RIPs including agrostin, gelonin, luffin,(More)
A microplate assay, for use with a variety of glycohydrolase enzymes, was developed to aid the screening of Chinese medicinal herb extracts for the presence of potential anti-viral and anti-lymphoma compounds. The microplate assay method described offers greater convenience, speed and reproducibility over existing methods. The enzymes tested were(More)
A multiple screening approach to detect compounds inhibitory to various aspects of the human immunodeficiency virus type 1 (HIV-1) life-cycle has been applied to aqueous extracts of 19 herbs traditionally used in Chinese medicine as anti-viral agents. The extracts were tested for their ability to inhibit HIV-1 in a series of in vitro assays. The extracts(More)
An improved method for the removal of polyphenolic compounds from aqueous extracts of plants is presented. The method removes > 99% polyphenolic compounds from 5 mg of extract. The method is simple, robust and reproducible. We examined the removal of polyphenolics from 5 different aqueous extracts of Chinese medicinal herbs.
A variant form of yeast pyruvate kinase (EC 2.7.1.40) with Ser-384 mutated to proline has been engineered in order to study the allosteric properties of this enzyme. Both the mutant and wild-type enzymes were overexpressed in a strain of yeast in which the genomic copy of the pyruvate kinase gene had been disrupted by an insertion of the Ura3 gene. Both(More)
Polysaccharopeptide (PSP) isolated from the edible mushroom Coriolus versicolor was tested for its potential as an anti-human immunodeficiency virus type 1 (HIV-1) compound in a series of in vitro assays. It demonstrated inhibition of the interaction between HIV-1 gp 120 and immobilized CD4 receptor (IC50 = 150 microg/ml), potent inhibition of recombinant(More)
A mutant form of pyruvate kinase in which serine 384 has been mutated to proline has been engineered in the yeast Saccharomyces cerevisiae. Residue 384 is located in a helix in a subunit interface of the tetrameric enzyme, and the mutation was anticipated to alter the conformation of the helix and hence destabilize the interface. Previous results indicate(More)
The enzyme from most sources is a tetramer of identical subunits each about 500 residues in length. The enzyme has an absolute requirement for monovalent and divalent cations (usually K+ and Mg2+) which act to coordinate and orientate the substrates prior to catalysis. A number of isoenzymes of pyruvate kinase are found to exist in vertebrate tissues. Their(More)
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