Biomedical subjects

G E Katzenstein

Publications and source records attributed to G E Katzenstein.

7 recordsLinked to original sources

PubMed1994

Mutation of the alpha 2 domain disulfide bridge of the class I molecule HLA-A*0201. Effect on maturation and peptide presentation.

A combination of saturation and site-directed mutagenesis was utilized to disrupt the alpha 2 domain disulfide bridge of HLA-A*0201. Mutation of cysteine 101 to a serine (C101S) or of cysteine 164 to alanine (C164A) decreased the rate of maturation of the heavy chain, the total amount of mature heavy chain within the cell, and the level of surface expression. Cells expressing these genes and loaded with a synthetic peptide derived from the influenza A matrix protein (58-66) were recognized poorly by HLA-A*0201-restricted, peptide-specific CTLs. Cells expressing mutant HLA-A*0201 loaded with a synthetic peptide derived from the HIV-1 pol protein (476-484) were not recognized by pol IV-9-specific CTLs. Mutant C164A cells infected with influenza virus were partially recognized by influenza matrix peptide-specific CTLs, while C101S cells were not lysed. Surprisingly, endogenous peptide loading of cells expressing mutant HLA-A*0201 using a minigene coding for either the influenza A matrix peptide 58-66, or HIV-1 pol peptide 476-484, resulted in efficient CTL recognition. This suggests different structural constraints for peptide binding in the endoplasmic reticulum during biosynthesis and for binding to exported molecules on the cells surface.

Amino Acid Sequence↗

PubMed1994

Binding of the protease-sensitive form of PrP (prion protein) to sulfated glycosaminoglycan and congo red [corrected].

Congo red and certain sulfated glycans are potent inhibitors of protease-resistant PrP accumulation in scrapie-infected cells. One hypothesis is that these inhibitors act by blocking the association between protease-resistant PrP and sulfated glycosaminoglycans or proteoglycans (e.g., heparan sulfate proteoglycan) that is observed in amyloid plaques of scrapie-infected brain tissue. Accordingly, we have investigated whether the apparent precursor of protease-resistant PrP, protease-sensitive PrP, binds to Congo red and heparin, a highly sulfated glycosaminoglycan with an inhibitory potency like that of heparan sulfate. Protease-sensitive PrP released from the surface of mouse neuroblastoma cells bound to heparin-agarose and Congo red-glass beads. Sucrose density gradient fractionation provided evidence that at least some of the PrP capable of binding heparin-agarose was monomeric. Free Congo red blocked PrP binding to heparin and vice versa, suggesting that these ligands share a common binding site. The relative efficacies of pentosan polysulfate, Congo red, heparin, and chondroitin sulfate in blocking PrP binding to heparin-agarose corresponded with their previously demonstrated potencies in inhibiting protease-resistant PrP accumulation. These results are consistent with the idea that sulfated glycans and Congo red inhibit protease-resistant PrP accumulation by interfering with the interaction of PrP with an endogenous glycosaminoglycan or proteoglycan.

Animals↗

PubMed1990

Secondary structure characteristics of proenkephalin peptides E, B, and F.

The conformations of three adrenal medullary enkephalin containing polypeptides (ECPs) were investigated to gain an understanding of their potential structure-activity relationships. Secondary structure characteristics of peptides E, B, and F were examined by circular dichrosim (CD) under conditions designed to mimic both the soluble state and the anisotropic environment which exists at the biological effector site. Conformational differences between the three peptides were further examined by Fourier Transform Infrared Spectroscopy (FTIR) and by empirical predictions for conformation and hydrophobic periodicity. Although all three peptides have a similar structure, existing in random configurations in aqueous solutions, they do exhibit unique individual potentials to assume secondary structure in less polar environments. These conformational differences may be important factors in determining their unique individual biological activities.

Adrenal Medulla↗

PubMed1987

Target tissue distribution of the proenkephalin peptides F, E, and B.

The adrenal medulla is a rich source of endogenous opioid peptides. These peptides exist predominantly in the form of larger (25-34 amino acid long) enkephalin containing peptides, whose biological roles have yet to be elucidated. We report here the tissue binding distribution of three iodinated enkephalin containing peptides, Peptides F, E, and B, in rats, rabbits, and guinea pigs following intravenous injection. Each [125I]peptide has a unique distribution profile but all three are found to bind to the pituitary in each species of animal examined. A number of lines of evidence point toward the enkephalin containing peptides, Peptides F, E, and B, having physiological roles distinct from the enkephalins. The distribution profile of these [125I]peptides reported here gives insight into their potential effector sites.

Animals↗

PubMed1986

Role of conformational changes in the elution of proteins from reversed-phase HPLC columns.

To test the hypothesis that conformational alterations might be involved in the elution of proteins from reversed-phase HPLC columns, the conformations of proteins bound onto a C-8 alkyl-bonded silica surface have been examined in the presence of increasing concentrations of the commonly employed eluent, 1-propanol. Using a combination of photoacoustic, diffuse reflectance deconvolution Fourier transform infrared and front face fluorescence spectroscopic techniques (to minimize interference from light scattering), the existence of surface-associated protein conformational changes induced by propanol is unequivocally demonstrated. The linear relationship found between the amount of propanol needed to elute proteins from C-8 columns and the midpoint of spectrally observed structural transitions is consistent with a role for conformational changes in the elution process.

1-Propanol↗

PubMed1985

Entropic DNA.

The presence of mobile genetic elements without apparent biological function within genomes requires explanation. It is argued that consideration of DNA as an open thermodynamic system leads to the simple hypothesis that mobile genetic material increases the internal entropy thereby lowering the free energy of the DNA relative to DNA of the same size. This phenomenon enhances the survival of such sequences by simple structural stabilization. The consequences of this idea are discussed in terms of the proposed Bekenstein limit to the entropy to energy ratio of thermodynamic systems and biological entropy/information flow.

Animals↗

PubMed1984

Protein conformation and reversed-phase high-performance liquid chromatography.

The structure of a series of proteins has been investigated by circular dichroism, fluorescence and visible spectroscopy as well as by differential scanning calorimetry under reversed-phase high-performance liquid chromatography elution conditions. These studies show that 1-propanol, a typical eluent, induces a reversible conformational change in proteins to an apparently ordered, helical form. This structural transition occurs in the range of propanol concentrations that produces elution of a particular protein. The possible relationship between this conformational change and protein elution is considered.

1-Propanol↗