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71.
Investigation of the polymorphic ScaI site by a PCR-based assay at the human atrial natriuretic peptides (hANP) gene locus 总被引:4,自引:0,他引:4
Rajendranath Ramasawmy Navaratnam Kotea Chang Yong Lu Chalom Sayada Sooriahnarain Baligadoo Rajagopal Krishnamoorthy 《Human genetics》1992,90(3):323-324
The ScaI polymorphic site within the stop codon of the human atrial natriuretic peptides (hANP) gene was investigated in Mauritian Indian, black African and French Caucasian populations. A distinct distribution pattern is observed in these three populations. 相似文献
72.
WT Ismaya A Efthyani DS Retnoningrum X Lai BW Dijkstra RR Tjandrawinata 《Biotechnic & histochemistry》2017,92(6):411-416
The light subunit of mushroom, Agaricus bisporus, tyrosinase (LSMT), has been identified as an extrinsic component of the enzyme. Its function is unknown, but it can cross an epithelial cell layer, which suggests that it can be absorbed by the intestine. A similar capability has been demonstrated for the HA-33 component of the progenitor toxin from Clostridium botulinum, which is the closest structural homolog of LSMT. Unlike HA-33, LSMT appears to be non-immunogenic as shown by preliminary tests in Swiss Webster mice. We investigated the immunogenicity and histopathology of LSMT in mice to determine its safety in vivo. LSMT did not evoke generation of antibodies after prolonged periods of intraperitoneal administration. Histopathological observations confirmed the absence of responses in organs after twelve weekly administrations of LSMT. We found that LSMT is not toxic and is less immunogenic than the C. botulinum HA-33 protein, which supports further research and development for pharmaceutical application. 相似文献
73.
R Martin DS Buchan JS Baker J Young N Sculthorpe FM Grace 《Biology of sport / Institute of Sport》2015,32(4):307-313
The present study examined the physiological impact of a school based sprint interval training (SIT) intervention in replacement of standard physical education (SPE) class on cardio-respiratory fitness (CRF) and glucose homeostasis during the semester following summer vacation. Participants (n=49) were randomly allocated to either intervention (SIT; n=26, aged 16.9 ± 0.3 yrs) or control group who underwent standard physical education (SPE; n=23, aged 16.8 ± 0.6 yrs). CRF (VO2max) and glucose homeostasis were obtained prior-to and following 7 weeks of SIT exercise. Significant group x time interaction was observed for CRF (P < 0.01) with non-significant trends for fasting insulin (P= 0.08), and HOMA-IR (P=0.06). CRF decreased (P < 0.01) in SPE such that POST intervention CRF was significantly lower (P< 0.05) in SPE. Fasting plasma glucose (P < 0.01), insulin (P< 0.01) and HOMA-IR (P< 0.01) increased significantly amongst SPE. The main finding of the present study is that 7-weeks of SIT exercise is an effective method of maintaining (but not improving) CRF and fasting insulin homeostasis amongst school-going adolescents. SIT exercise demonstrates potential as a time efficient physiological adjunct to standard PE class in order to maintain CRF during the school term. 相似文献
74.
Two soluble glycosyltransferases glycosylate less efficiently in vivo than their membrane bound counterparts 总被引:1,自引:1,他引:1
Zhu G; Allende ML; Jaskiewicz E; Qian R; Darling DS; Worth CA; Colley KJ; Young WW Jr 《Glycobiology》1998,8(8):831-840
Many Golgi glycosyltransferases are type II membrane proteins which are
cleaved to produce soluble forms that are released from cells. Cho and
Cummings recently reported that a soluble form of alpha1, 3-
galactosyltransferase was comparable to its membrane bound counterpart in
its ability to galactosylate newly synthesized glycoproteins (Cho,S.K. and
Cummings,R.D. (1997) J. Biol. Chem., 272, 13622-13628). To test the
generality of their findings, we compared the activities of the full length
and soluble forms of two such glycosyltransferases, ss1,4
N-Acetylgalactosaminyltransferase (GM2/GD2/ GA2 synthase; GalNAcT) and beta
galactoside alpha2,6 sialyltransferase (alpha2,6-ST; ST6Gal I), for
production of their glycoconjugate products in vivo . Unlike the full
length form of GalNAcT which produced ganglioside GM2 in transfected cells,
soluble GalNAcT did not produce detectable GM2 in vivo even though it
possessed in vitro GalNAcT activity comparable to that of full length
GalNAcT. When compared with cells expressing full length alpha2,6-ST, cells
expressing a soluble form of alpha2,6-ST contained 3-fold higher
alpha2,6-ST mRNA levels and secreted 7-fold greater alpha2,6-ST activity as
measured in vitro , but in striking contrast contained 2- to 4-fold less of
the alpha2,6-linked sialic acid moiety in cellular glycoproteins in vivo .
In summary these results suggest that unlike alpha1,3-galactosyltransferase
the soluble forms of these two glycosyltransferases are less efficient at
glycosylation of membrane proteins and lipids in vivo than their membrane
bound counterparts.
相似文献
75.
Free radical reactions of Martynoside (MAR), a phenylpropanoid glycoside, with a variety of oxidants were studied in the aqueous solution by laser photolysis and pulse radiolysis techniques. The pK
avalue of MAR in aqueous solution was measured from the pH dependent changes of the UV absorption at 384 nm with value of pKa=9.2. The phenoxyl radical of MAR which exhibits maximum absorption at 360 nm was generated by one-electron transfer to N3&bull• or Br2• properties of phenoxyl radical such as extinction coefficient, formation and decay rate constants were also determined. The reaction rate constant of O2•la>k=8.5×104 dm3 · mol--1 · s--1, was measured by the method of competition kinetics. By measuring time-resolved luminescence emission at 1270 nm, the quenching rate constant of singlet oxygen by MAR was obtained to be 3.3×10
6dm
3· mol
-1· s
-1. Reduction potential of the MAR couple (MAR
•/MAR), determined using rutin as reference compound, gave a value E=0.66 V vs. NHE. The antioxidative properties of MAR were compared with those of some well-known antioxidants. 相似文献
76.
Optimization of apolipoprotein B mRNA editing by APOBEC1 apoenzyme and the role of its auxiliary factor, ACF 总被引:2,自引:0,他引:2 下载免费PDF全文
Expression and purification to homogeneity of the apolipoprotein B mRNA editing subunit, APOBEC1, has allowed the demonstration that this apoenzyme has considerable residual enzymatic activity on a minimal apoB mRNA substrate, even in the absence of any auxiliary factors. Assay of this activity as a function of various experimental conditions has led to substantial optimization of assay conditions through the use of incomplete factorial and response surface experiments. Surprisingly, the apoenzyme is thermostable, and has a temperature optimum near 45 degrees C. We have used these optimized conditions, to assess steady-state kinetic parameters for APOBEC1 mRNA editing activity with and without the auxiliary factor, ACF. An important effect of the auxiliary factor is to broaden the temperature range of APOBEC1 activity, lowering the optimal temperature and enabling it to function optimally at lower temperatures. A model consistent with this observation is that at lower temperatures ACF promotes a conformational transition in the RNA substrate that occurs spontaneously at higher temperature. Notably, the substantial RNA editing activity of APOBEC1 alone may be responsible for the "hyperediting" observed upon overexpression of APOBEC1 in transgenic mice. 相似文献
77.
The apolipoprotein B mRNA editing complex performs a multifunctional cycle and suppresses nonsense-mediated decay 总被引:3,自引:0,他引:3 下载免费PDF全文
Chester A Somasekaram A Tzimina M Jarmuz A Gisbourne J O'Keefe R Scott J Navaratnam N 《The EMBO journal》2003,22(15):3971-3982
The C to U editing of apolipoprotein B (apoB) mRNA is mediated by a minimal complex composed of an RNA-binding cytidine deaminase (APOBEC1) and a complementing specificity factor (ACF). This editing generates a premature termination codon and a truncated open reading frame. We demonstrate that the APOBEC1-ACF holoenzyme mediates a multifunctional cycle. The atypical APOBEC1 nuclear localization signal is involved in RNA binding and is used to import ACF into the nucleus as cargo. APOBEC1 alone induces nonsense-mediated decay (NMD). The APOBEC1-ACF complex edits and remains associated with the edited RNA to protect it from NMD. The APOBEC1 nuclear export signal is involved in the export of ACF and the edited apoB mRNA together, to the site of translation. 相似文献
78.
Evidence from extended X-ray absorption fine structure and site-specific mutagenesis for zinc fingers in UvrA protein of Escherichia coli 总被引:6,自引:0,他引:6
S Navaratnam G M Myles R W Strange A Sancar 《The Journal of biological chemistry》1989,264(27):16067-16071
The UvrA protein is the damage recognition subunit of the Escherichia coli repair enzyme ABC excision nuclease. Sequence analysis of this 940-amino acid protein revealed two regions of sequence homology to the zinc finger motif found in many DNA binding proteins. Physical and chemical analyses indicate about 2 zinc atoms/molecule. We have used extended x-ray absorption fine structure analysis to demonstrate that each of these zinc atoms is coordinated with 4 cysteine residues at a distance of 2.32 +/- 0.2 A. Substitution of one of the cysteines by a histidine, a serine, or an alanine in one of the potential finger sites resulted in a respective decrease in complementing activity. We thus conclude that the two zinc fingers identified by sequence analysis do indeed have zinc finger structure in UvrA protein. 相似文献
79.
80.
S Foley S Navaratnam D J McGarvey E J Land T G Truscott C A Rice-Evans 《Free radical biology & medicine》1999,26(9-10):1202-1208
The singlet oxygen quenching rate constants (kq) for a range of hydroxycinnamic acids in acetonitrile and D2O solutions were measured using time resolved near infrared phosphorescence in order to establish their antioxidant activity. The magnitude of kq observed depends on both the nature of the substituent groups and solvent polarity. The variations in kq depend on the energy of the hydroxycinnamic acid/molecular oxygen charge transfer states, (O2delta- ...HCAdelta+). In D2O the values of kq range from 4x10(7) M(-1) s(-1) to 4x10(6) M(-1) s(-1) for caffeic acid and o-coumaric acid respectively. In acetonitrile, the charge transfer energy levels are raised and this is reflected in lower singlet oxygen quenching rate constants with a kq value of 5x10(6) M(-1) s(-1) for caffeic acid. The phenoxyl radical spectra derived from the hydroxycinnamic acids were determined using pulse radiolysis of aqueous solutions and the reduction potentials were found to range from 534 to 596 mV. A linear correlation is observed between reduction potential, and hence free energy for electron transfer, and log kq. These correlations suggest a charge transfer mechanism for the quenching of singlet oxygen by the hydroxycinnamic acids. 相似文献