The synthesis of protected 5''-amino-2'',5''-dideoxyribonucleoside-3''-O-phosphoramidites; applications of 5''-amino-oligodeoxyribonucleotides.

Synthetic routes to the four appropriately protected 5'-amino-2',5'-dideoxyribonucleoside-3'-O-(2-cyanoethyl N,N-diisopropylphosphoramidites) have been developed. The structures of all intermediates were confirmed by 13C n.m.r. spectroscopy. These building blocks have been used to prepare 5'-amino-oligodeoxyribonucleotides, which can be coupled to a wide variety of compounds, in particular metal cluster derivatives, but also fluorophores and biotin derivatives, thus generating a variety of very useful probes. Brief mention is made of a tetrairidium cluster derivative of 5'-amino-d[CCGATATCGG], which has been cocrystallised with EcoRV, and will be used for electron microscopy studies.     

The synthesis of protected 5''-mercapto-2'',5''-dideoxyribonucleoside-3''-O-phosphoramidites; uses of 5''-mercapto-oligodeoxyribonucleotides.

The syntheses of the four novel, base protected 5'-(S-triphenylmethyl)mercapto-2',5'-dideoxyribonucleoside-3 '-O-(2-cyanoethyl N,N-diisopropylphosphoramidites) are described. These compounds have been used to prepare 5'-(S-triphenylmethyl) mercapto-oligodeoxyribonucleotides, which are readily purified by reversed phase h.p.l.c., owing to the highly lipophilic trityl group. After cleavage of the S-trityl group by silver or mercuric ions, the free thiol moiety can be coupled to a wide variety of reagents, generating very useful probes. Fluorescent labelled 5'-mercapto-oligodeoxyribonucleotides are being used for automated DNA sequencing without radioactivity, and heavy metal labelled 5'-mercapto-oligonucleotides will be used in X-ray crystallography.     

Inactivation of liver 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase by o-phthalaldehyde.

The two activities of chicken liver 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase were inactivated by o-phthalaldehyde. Absorbance and fluorescence spectra of the modified enzyme were consistent with the formation of an isoindole derivative (1 mol/mol of enzyme subunit). The inactivation of 6-phosphofructo-2-kinase by o-phthalaldehyde was faster than the inactivation of fructose-2,6-bisphosphatase, which was concomitant with the increase in fluorescence. The substrates of 6-phosphofructo-2-kinase did not protect the kinase against inactivation, whereas fructose-2,6-bisphosphate fully protected against o-phthalaldehyde-induced inactivation of the bisphosphatase. Addition of dithiothreitol prevented both the increase in fluorescence and the inactivation of fructose-2,6-bisphosphatase, but not that of 6-phosphofructo-2-kinase. It is proposed that o-phthalaldehyde forms two different inhibitory adducts: a non-fluorescent adduct in the kinase domain and a fluorescent isoindole derivative in the bisphosphatase domain. A lysine and a cysteine residue could be involved in fructose-2,6-bisphosphate binding in the bisphosphatase domain of the protein.     

Rod/cone dysplasia in Irish setters. Presence of an altered rhodopsin.

The subcellular distribution of beta-glucuronidase acquired by deficient human fibroblasts during co-culture with peritoneal macrophages was compared with that taken up by receptor-mediated endocytosis. Labelled enzyme taken up via receptors was located initially in a low-density endosomal fraction and was transferred to lysosomes within a few minutes. The beta-glucuronidase acquired during 24 h of co-culture was present almost entirely within lysosomes and had a distribution profile identical with that of endogenous beta-hexosaminidase. Monensin prevented transfer of radiolabelled enzyme from endosomes to lysosomes and had a similar effect on the distribution of enzyme acquired by direct transfer, causing beta-glucuronidase to accumulate within endosomes. When the temperature was lowered from 37 degrees C to 19 degrees C, the rate of transfer of enzyme from endosomes to lysosomes was decreased during both direct transfer and indirect receptor-mediated endocytosis. These results show that a lysosomal enzyme acquired by direct transfer during cell-to-cell contact follows a similar intracellular route and has a similar distribution to that of enzymes taken up via cell-surface receptors.     

Evolutionary conservation of the chromosomal configuration and regulation of amylase genes among eight species of the Drosophila melanogaster species subgroup

Nuclear DNA was extracted from each of the eight species comprising the Drosophila melanogaster species subgroup. Southern hybridization of this DNA by using a molecular probe specific for the alpha-amylase coding region showed that the duplicated structure of the amylase locus, first found in D. melanogaster, is conserved among all species of the melanogaster subgroup. Evidence is also presented for the concerted evolution of the duplicated genes within each species. In addition, it is shown that the glucose repression of amylase gene expression, which has been extensively studied in D. melanogaster, is not confined to this species but occurs in all eight members of the species subgroup. Thus, both the duplicated gene structure and the glucose repression of Drosophila amylase gene activity are stable over extended periods of evolutionary time.      

Regulation of fructose 2,6-bisphosphate concentration in white adipose tissue.

Injection of insulin to fed rats diminished the concentration of fructose 2,6-bisphosphate in white adipose tissue. Incubation of epididymal fat-pads or adipocytes with insulin stimulated lactate release and sugar detritiation and also decreased fructose 2,6-bisphosphate concentration. Such a decrease was, however, not observed in fat-pads from starved or alloxan-diabetic rats. Incubation of adipocytes from fed rats with various concentrations of glucose or fructose led to a dose-dependent rise in fructose 2,6-bisphosphate which correlated with lactate output and detritiation of 3-3H-labelled sugar. In adipocytes from fed rats, palmitate stimulated the detritiation of [3-3H]glucose without affecting lactate production and fructose 2,6-bisphosphate concentration. Incubation of epididymal fat-pads from fed rats in the presence of antimycin stimulated lactate output but decreased fructose 2,6-bisphosphate concentration. Changes in lipolytic rates brought about by noradrenaline, insulin, adenosine and corticotropin in adipocytes from fed rats were not related to changes in fructose 2,6-bisphosphate or to rates of lactate output. In fed rats, the activity of 6-phosphofructo-2-kinase was not changed after treatment of adipocytes with insulin, noradrenaline or adenosine. It is suggested that the decrease in fructose 2,6-bisphosphate concentration observed after insulin treatment can be explained by the increase in sn-glycerol 3-phosphate, an inhibitor of 6-phosphofructo-2-kinase.     

Phosphorylation of purified bovine heart and rat liver 6-phosphofructo-2-kinase by protein kinase C and comparison of the fructose-2,6-bisphosphatase activity of the two enzymes.

Purified bovine heart 6-phosphofructo-2-kinase can be phosphorylated in the presence of protein kinase C and dephosphorylated by alkaline phosphatase; changes in phosphorylation state have no effect on enzyme activity. By contrast, the rat liver enzyme is a poor substrate for protein kinase C. Unlike the liver enzyme, which is bifunctional and is phosphorylated by fructose 2,6-[2-32P]bisphosphate, the heart enzyme contains 10 times less fructose 2,6-bisphosphatase activity and is phosphorylated at a slower rate and to a lesser extent than the liver enzyme. Both rat liver and bovine heart enzymes catalyse a similar exchange reaction between [U-14C]ADP and ATP.