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Biomedical subjects

K L LaMarco

Publications and source records attributed to K L LaMarco.

11 recordsLinked to original sources
PubMed1989

Purification of a set of cellular polypeptides that bind to the purine-rich cis-regulatory element of herpes simplex virus immediate early genes.

Expression of herpes simplex virus type 1 (HSV1) immediate early (IE) genes is activated by a polypeptide component of the mature virion termed viral protein 16 (VP16). Stimulation of IE expression by VP16 operates via two cis-regulatory sequences: TAATGARAT, and the purine-rich hexanucleotide sequence GCGGAA. VP16 does not bind directly to either of the IE cis-regulatory sequences. Rather, these elements appear to represent binding sites for host cell proteins. Herein, we report the purification of a host cell factor that binds to the GCGGAA motif. We show further that this factor is capable of binding in vitro to an oligomerized form of the hexanucleotide sequence GAAACG, which is common to a variety of virus- and interferon-inducible genes. The GAAACG repeats of interferon- and virus-inducible genes, and the GA-rich repeats of HSV1 IE genes confer similar functional properties when appended to the promoter of a heterologous gene. These observations raise the possibility that HSV1 may activate its IE genes in a manner that exploits one of the components used by mammalian cells to combat virus infection.

Animals↗
PubMed1988

Evidence of DNA: protein interactions that mediate HSV-1 immediate early gene activation by VP16.

The viral genes first expressed upon lytic infection by herpes simplex virus type 1 (HSV-1) encode the five immediate early (IE) proteins. IE gene expression is potently and specifically induced by a virion protein termed VP16. Previous studies have shown that the activating properties of VP16 are IE gene specific and mediated by upstream regulatory elements common to each IE gene. Paradoxically, however, VP16 does not appear to be a sequence-specific DNA-binding protein. To understand the specificity of VP16 activation, we identified the cis-regulatory sequences of an IE gene that mediate VP16 response. Two distinct DNA sequence motifs enable the ICP4 gene to respond to VP16. Biochemical fractionation of nuclear proteins from uninfected cells revealed the existence of cellular proteins that bind directly to each of these VP16 cis-response elements. These observations, in concert with the identification of functional domains of the VP16 protein, lead to the hypothesis that VP16 achieves activation specificity via protein: protein, rather than protein: DNA, interactions.

Base Sequence↗
PubMed1988

In situ detection of sequence-specific DNA binding activity specified by a recombinant bacteriophage.

We have used a recombinant bacteriophage that expresses the DNA-binding domain of C/EBP to optimize conditions for a screening technique that may facilitate the cloning of genes that encode sequence-specific DNA-binding proteins. The method relies on the expression of cDNA inserts in bacteriophage lambda gt11. Fusion protein adsorbed onto nitrocellulose filters is probed with radioactive, double-stranded DNA as a ligand. Two procedures greatly increase the level of binding between ligand and recombinant fusion protein. First, nitrocellulose filters are processed through a denaturation/renaturation regimen using 6 M guanidine hydrochloride. Second, synthetic DNA corresponding to the specific binding site is catenated extensively using DNA ligase. The combination of these procedures leads to remarkably strong detection signals. Specific DNA-binding signals can be detected on duplicate filters, and filters can be washed and reused by repeating the cycle of denaturation/renaturation.

Animals↗
PubMed1987

Pseudo-Gaucher cells in the bone marrow of a patient with Hodgkin's disease.

The authors studied an 18-year-old woman with stage IIIB nodular sclerosis Hodgkin's disease whose bone marrow contained abnormal storage cells that resembled Gaucher cells by light microscopic examination ("pseudo-Gaucher" cells). Electron microscopic examination revealed that these cells differed from true Gaucher cells and resembled storage cells previously described in chronic myelogenous leukemia. The patient's peripheral blood leukocyte beta-glucosidase and serum acid phosphatase levels were elevated, ruling out the diagnosis of inherited Gaucher's disease. After treatment with six monthly cycles of systemic chemotherapy (nitrogen mustard, vincristine, procarbazine, bleomycin, doxorubicin, and prednisone), all signs of Hodgkin's disease and pseudo-Gaucher cells disappeared. Repeat leukocyte beta-glucosidase and serum acid phosphatase levels were unchanged. The present case is unique with its documentation of classical enzyme patterns for beta-glucosidase and acid phosphatase and electron microscopic features. The authors postulate that pseudo-Gaucher cells result from excessive cell breakdown with an overload of available beta-glucosidase.

Acid Phosphatase↗
PubMed1986

Hydrolysis of a naturally occurring beta-glucoside by a broad-specificity beta-glucosidase from liver.

We have isolated from guinea-pig liver a broad-specificity beta-glucosidase of unknown function that utilizes as its substrate non-physiological aryl glycosides (e.g. 4-methylumbelliferyl beta-D-glucopyranoside, p-nitrophenyl beta-D-glucopyranoside). The present paper documents that this enzyme can be inhibited by various naturally occurring glycosides, including L-picein, dhurrin and glucocheirolin. In addition, L-picein, which acts as a competitive inhibitor of the broad-specificity beta-glucosidase (Ki 0.65 mM), is also a substrate for this enzyme (Km 0.63 mM; Vmax. 277,000 units/mg). Heat-denaturation, kinetic competition studies, chromatographic properties and pH optima all argue strongly that the broad-specificity beta-glucosidase is responsible for the hydrolysis of both the non-physiological aryl glycosides and L-picein. This paper demonstrates that beta-glucosidase can catalyse the hydrolysis of a natural glycoside, and may provide a key to understanding the function of this enigmatic enzyme. A possible role in the metabolism of xenobiotic compounds is discussed.

Animals↗
PubMed1985

Properties of an acid phosphatase from Legionella micdadei which blocks superoxide anion production by human neutrophils.

The high-speed supernatant (100,000 g, 1 h) obtained after centrifuging a suspension of Legionella micdadei that had been freeze-thawed and sonicated contained (i) considerable acid phosphatase activity when assayed using 4-methylumbelliferyl phosphate (MUP) as the substrate, and a factor that blocked superoxide anion production by human neutrophils stimulated with f-Met-Leu-Phe. Chromatography of the extract on a hydroxylapatite column resolved two acids phosphatases (designated ACP1 and ACP2). Subsequent chromatography of ACP2 on a Sephadex G-150 column revealed coincident elution of phosphatase activity and neutrophil blocking activity. When heated at 45 degrees C for various periods of time, the phosphatase activity of the acid phosphatase preparation was lost at the same rate as the ability of the preparation to block superoxide anion production by neutrophils. Furthermore, preincubation of neutrophils and acid phosphatase together in the presence of a heteropolymolybdate complex that inhibits the phosphatase eliminated the effect of the L. micdadei phosphatase on neutrophil superoxide anion production. ACP2 had the following properties: pH optimum, 6.0; Km for MUP, 3.8 mM; isoelectric point, 4.5; substrate specificity, MUP greater than ADP greater than phosphoenolpyruvate greater than phosphothreonine greater than phosphoserine greater than phosphotyrosine; molecular weight (estimated by sucrose density gradient centrifugation and gel filtration chromatography), 71,000-86,000. These results indicate that a cell-associated phosphatase may play a role in the virulence of L. micdadei.

Acid Phosphatase↗
PubMed1985

Galactosylsphingosine inhibition of the broad-specificity cytosolic beta-glucosidase of human liver.

Glucosylsphingosine is a potent inhibitor of lysosomal glucocerebrosidase and the broad-specificity, cytosolic beta-glucosidase of human liver. In the present study, it was demonstrated that the broad-specificity beta-glucosidase was also inhibited by galactosylsphingosine. The inhibition was observed when the enzyme was assayed for beta-glucosidase, beta-galactosidase, beta-xylosidase, and alpha-arabinosidase activities. Inhibition was of the mixed-type and the degree of inhibition depended on the substrate. For example, galactosylsphingosine was a more potent inhibitor of beta-glucosidase activity (I0.5 = 0.3 mM) than beta-xylosidase activity (I0.5 = 1.2 mM). In addition, the observation that the broad-specificity, cytosolic beta-glucosidase was inhibited by hydrophobic glycosphingolipids prompted the definition of a revised purification procedure which took advantage of hydrophobic affinity chromatography. This revised purification scheme employed Octyl-Sepharose and yielded the largest (68,000 Da) and most active (470,000 nmol h-1 mg protein-1) beta-glucosidase preparation yet described. The beta-glucosidase preparation contained 19% serine and 17% glycine, while 24% of the total amino acids were hydrophobic. The results of this study document the presence of a sphingolipid binding site on the broad-specificity beta-glucosidase. The implications of galactosylsphingosine inhibition of cytosolic beta-glucosidase and the possible role of the enzyme in glycosphingolipid metabolism are discussed.

Amino Acids↗
PubMedDate not supplied

Neuraminidase activity in middle ear effusions.

Analyses of Streptococcus pneumoniae culture filtrates and middle ear effusions (MEE) containing S pneumoniae for various hydrolytic enzymes have demonstrated substantial levels of neuraminidase activity when measured employing a sensitive fluorometric assay. S pneumoniae neuraminidase exhibits optimum activity near neutral pH (6.0 to 6.5), and catalyzes the cleavage of sialic acid residues from glycoproteins, gangliosides and mucopolysaccharides. S pneumoniae begins secreting large amounts of neutral neuraminidase (mean [means] = 43.3 units/mL culture filtrate) when cells enter the stationary phase. Nearly all (96%) human chronic MEEs yielding positive cultures for S pneumoniae contain neuraminidase activity (means = 0.200 units/mg protein), while only 21.1% to 45.5% of all other effusions contain the enzyme. Middle ear effusions obtained from S pneumoniae infected-chinchillas contained large amounts of neuraminidase activity (approximately 200 units/mL), which decayed exponentially in vivo with an apparent half-life of 8 1/2 days. Three neuraminidase isoenzymes (designated I-III) were identified in S pneumoniae culture filtrates, as well as in MEEs from chinchillas infected with the organism, using a combination of ion-exchange and gel filtration chromatography. With 4-methylumbelliferyl-N-acetylneuraminic acid serving as substrate, preparation I from both culture filtrates and MEEs was characterized by a high Michaelis constant (Km), while forms II and III had low Km values. Preferred substrates were orosomucoid and neuramin-lactose; gangliosides, thyroglobulin, and bovine submaxillary mucin were poorer substrates.

Animals↗
PubMedDate not supplied

Experimental alteration of chinchilla middle ear mucosae by bacterial neuraminidase.

Streptococcus pneumoniae secretes a variety of extracellular glycosidase including a neuraminidase which has been found in middle ear effusion from patients with both acute and chronic otitis media. This enzyme cleaves sialic acid from membrane glycoproteins, thereby exposing galactose residues, the penultimate sugar. The ability of partially purified neuraminidase to alter the middle ear mucosa was investigated in the chinchilla. After incubation with neuraminidase, chinchilla middle ears were removed and exposed to galactose residues labeled with tritium. Membrane glycoproteins were solubilized and separated according to molecular weight by sodium dodecylsulfate electrophoresis. Increases in tritium incorporation, when compared to control incubations, indicated that galactose residues had been exposed and sialic acid residues removed from glycoproteins of both high and low molecular weight. Such membrane destruction could contribute significantly to the pathology of otitis media with effusion.

Animals↗
PubMedDate not supplied

Hydrolase activity in acute otitis media with effusion.

Biochemical studies of middle ear effusions (MEE) from patients with chronic or recurrent otitis media with effusion (OME) have demonstrated the presence of significant levels of certain hydrolytic and oxidative enzymes. We have examined MEE from patients with acute OME for the content of a number of lysosomal hydrolases and find no significant differences in the mean values for acid phosphatase, alpha-mannosidase, beta-galactosidase, beta-glucuronidase, hexosaminidase, and neuraminidase between purulent and serous effusions. In every case, the mean activities of these enzymes were greater in culture-positive than in culture-negative effusions although this difference was significant only in the case of neuraminidase. Neuraminidase activity was detected in 78% of those MEEs from which Streptococcus pneumoniae could be cultured and in only 32% to 64% of all other effusions. No correlation was observed between the level of neuraminidase released into the extracellular growth medium and the infectivity of various strains of S pneumoniae.

Acute Disease↗