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1.
Comparison of bone marrow extracellular matrices. 总被引:1,自引:0,他引:1
M Lee I P Christopherson J M Lehman C J Bennett H T Cheung 《Biochimica et biophysica acta》1999,1428(2-3):300-304
We have compared the structure and composition of adult and fetal bovine bone marrow extracellular matrices. In contrast to fetal bone marrow, adult bone marrow has more oval fenestration and accumulation of adipocytes as well as lower protein content. These differences could be due to remodeling of bone marrow tissue as it develops. Zymogram analysis of matrix metalloproteinase (MMP) and tissue inhibitor of MMP (TIMP) activities showed that fetal, but not adult bone marrow extract contained a 96-kDa MMP and TIMP-1 and -2. These activities may contribute to the structural differences between adult and fetal bone marrow tissues. 相似文献
2.
M N Lorenzo R Y Khan Y Wang S C Tai G C Chan A H Cheung P A Marsden 《Biochimica et biophysica acta》2001,1522(1):46-52
Generation of the functionally pleiotropic members of the endothelin vasoactive peptide family is critically catalyzed by unique type II metalloproteases, termed endothelin converting enzymes (ECE). Isolation of human ECE-2 (EC 3.4.24.71) cDNAs revealed deduced open reading frames of 787 and 765 amino acids with approximately 60% identity with human ECE-1. Characterization of mRNA variants revealed mRNA structural diversity at the 5'-terminus. Two mRNA species exist containing distinct first and second exons. Furthermore, in one of these species, an in-frame deletion of the intracytoplasmic domain removed 29 amino acids. Because of the previously reported human genetic diseases ascribed to germline mutations of member genes of the endothelin family, ECE2 was localized in human chromosomes with fluorescence in situ hybridization and radiation hybrid mapping to 3q28-q29 and SHGC-20171/D3S1571, respectively. 相似文献
3.
The addition of 0.167 to 4.0 mM cAMP to gel-filtered rabbit reticulocyte lysates stimulates the initial rate and the extent of polypeptide synthesis. The stimulation is at the initiation step of polypeptide synthesis as measured by the (i) increased dipeptide, methionyl-valine, accumulation in the presence of the specific initiation inhibitor, pactamycin, and (ii) increased formation of the 40 S and 80 S initiation complex when gel-filtered lysates are incubated with [35S]Met-tRNAFMet. Furthermore, a synergistic stimulation of protein synthesis is observed when cAMP and hexose phosphates (which alone elicit a 1.8-fold stimulation of protein synthesis) are added simultaneously to gel-filtered rabbit reticulocyte lysates. These results indicate that cAMP and hexose phosphates are both essential to maintain the high rate of initiation. 相似文献
4.
M A Winkler V A Fried D L Merat W Y Cheung 《The Journal of biological chemistry》1987,262(32):15466-15471
Calmodulin and calmodulin complexed with calcineurin phosphatase were trace labeled with [3H]acetic anhydride and the incorporation of [3H]acetate into each epsilon-amino lysine of calmodulin was measured. The relative reactivities of calmodulin lysines were higher in the presence of Ca2+ than in the presence of EGTA, and the order was: Lys-75 greater than Lys-94 greater than Lys-148 greater than or equal to Lys-77 greater than Lys-13 greater than or equal to Lys-21 greater than Lys-30. The changes in relative reactivity implied a change in conformation. When calmodulin was complexed with the phosphatase, Lys-21, Lys-77, and Lys-148 were most protected, implying that these residues are at or near the interaction sites or are conformationally perturbed by the interaction. Lys-30 and Lys-75 were slightly protected, lysine 13 showed no change, while lysine 94 significantly increased in reactivity. Comparison with results obtained from myosin light chain kinase using a similar technique (Jackson, A. E., Carraway, K. L., III, Puett, D., and Brew, K. (1986) J. Biol. Chem. 261, 12226-12232) reveals that calmodulin may interact with each of the two enzymes similarly at or near Lys-21, Lys-75, and Lys-148; one difference with phosphatase is that complex formation also involved Lys-77. These findings suggest that calmodulin interacts differently with its target enzymes. 相似文献
5.
Increased reactivity in the mesenteric artery of spontaneously hypertensive rats to phorbol ester 总被引:1,自引:0,他引:1
The contraction responses of mesenteric artery from 10 week old spontaneously hypertensive rats (SHRs) and normotensive Wistar Kyoto controls (WKYs) to phorbol 12, 13 - dibutyrate (PDBu) and agents acting on the potential-operated calcium channels were compared. The vessels from the SHR were significantly more sensitive to PDBu than those from the WKY. The PDBu-induced contractions were inhibited by nifedipine. The vessels from the SHR were also more sensitive to Bay K 8644 and KCl than the WKY. Low concentrations of PDBu (1 nM) potentiated the KCl contraction significantly more in the SHR than the WKY. It is suggested that the increased reactivity to PDBu in the SHR may in part be related to changes in the activity of the potential-operated calcium channels. 相似文献
6.
We have determined the free energy of formation of the binary complexes formed between skeletal troponin C and troponin T (TnC.TnT) and between troponin T and troponin I (TnT.TnI). This was accomplished by using TnC fluorescently modified at Cys-98 with N-(iodoacetyl)-N'-(5-sulfo-1-naphthyl)ethylenediamine for the first complex and TnI labeled at Cys-133 with the same probe for the other complex. The free energy of the ternary complex formed between troponin C and the binary complex TnT.TnI [TnC.(TnT.TnI)] was also measured by monitoring the emission of 5-(iodoacetamido)eosin attached to Cys-133 of the troponin I in TnT.TnI. The free energies were -9.0 kcal.mol-1 for TnC.TnT, -9.2 kcal.mol-1 for TnT.TnI, and -8.7 kcal.mol-1 for TnC.(TnT.TnI). In the presence of Mg2+ the free energies of TnC.TnT and TnC.(TnT.TnI) were -10.3 and -10.9 kcal.mol-1, respectively; in the presence of Ca2+ the corresponding free energies were -10.6 and -13.5 kcal.mol-1. Mg2+ and Ca2+ had negligible effect on the free energy of TnT.TnI. From these results the free energies of the formation of troponin from the three subunits were found to be -16.8 kcal.mol-1, -18.9 kcal.mol-1, and -21.6 kcal.mol-1 in the presence of EGTA, Mg2+, and Ca2+, respectively. Most of the free energy decrease caused by Ca2+ binding to the Ca2+-specific sites is derived from stabilization of the TnI-TnC linkage.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
7.
Isolation and characterization of a collagen fibril-associated dermatan sulphate proteoglycan from bovine lung 总被引:1,自引:0,他引:1
T H van Kuppevelt H M Janssen H M van Beuningen K S Cheung M M Schijen C M Kuyper J H Veerkamp 《Biochimica et biophysica acta》1987,926(3):296-309
Dermatan sulphate proteoglycans have been extracted from bovine lung with 2.0 M CaCl2 and isolated using CsCl density gradient centrifugation, DEAE ion-exchange chromatography, gel chromatography and preparative sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Ultrastructurally these proteoglycans are specifically associated with collagen fibrils. Dermatan sulphate (Mr 15.10(3)-35.10(3), with a strong prevalence for the higher Mr) is link via an O-glycosidic bond to a protein core, which is rich in Asx, Glx and Leu. Of the total uronic acid, 91% is iduronic acid. A part of the glucuronic acid residues is located near the protein core and a large cluster of disaccharides is devoid of glucuronic acid residues. An inhibition enzyme immunoassay has been developed to quantitate the proteoglycan. A model for the interaction between dermatan sulphate proteoglycans and collagen fibrils is proposed. 相似文献
8.
DNA nucleotide sequence analysis of the immediate-early gene of pseudorabies virus. 总被引:29,自引:4,他引:25 下载免费PDF全文
A K Cheung 《Nucleic acids research》1989,17(12):4637-4646
The complete DNA sequence coding for the immediate-early protein (IE180) of pseudorabies virus was determined. The coding region of IE180 is 4380 nucleotides for 1460 amino acid residues. G+C content of the non-coding portion of the IE gene is 70.3% while the G+C content of the coding portion is considerably higher at 80.1%. Correspondingly, codons consisting mainly of Gs and Cs are favoured. Clusters of amino acid homologies are observed among IE180 of pseudorabies virus, ICP4 of herpes simplex virus type-1 and IE140 of varicella-zoster virus, and are organized similarly in all three polypeptides. Functions exhibited by IE180 are assigned, tentatively, to structural domains of the molecule by analogy to the HSV-1 ICP4 polypeptide. 相似文献
9.
A Cheung J A Engelke C Sanders J W Suttie 《Archives of biochemistry and biophysics》1989,274(2):574-581
The liver microsomal vitamin K-dependent carboxylase catalyzes the post-translational conversion of specific glutamyl to gamma-carboxyglutamyl (Gla) residues in precursor forms of a limited number of proteins. These proteins contain an amino-terminal extension (propeptide) that is presumed to serve as an enzyme recognition site to assure their normal processing. The free, noncovalently bound propeptide has also been shown to stimulate the in vitro activity of this enzyme. This peptide has now been shown to lower the app Km of a low-molecular-weight Glu site substrate while having no influence on the app Km of the other substrates, vitamin KH2, O2, and CO2/HCO3-. Propeptide addition was shown to have no influence on the ratio of the two products of the enzyme, Gla and vitamin K-2,3-epoxide. Stimulation of carboxylase activity by the propeptide from human factor X was observed in a number of rat tissues and in the liver of a number of different species. Stability of the enzyme in crude microsomal preparations was greatly enhanced by the presence of propeptide. These observations are consistent with the hypothesis that this region of the protein substrates for the carboxylase not only serves an enzyme recognition or docking function but also modulates the activity of the enzyme by altering the affinity for one of its substrates. 相似文献
10.
The disordered production of inorganic pyrophosphate (PPi) by articular cartilage is thought to have an important role in the pathogenesis of calcium pyrophosphate dihydrate deposition disease and perhaps osteoarthritis. We have previously shown that fetal calf serum added to the culture media of porcine articular cartilage explants increases the elaboration of PPi into the ambient media. We have examined this PPi stimulatory activity by studying the effects of adult human serum (HS), serum derived from adult human plasma (HP), and an acid-alcohol extract of human platelets (PE) on PPi production in cartilage organ culture. Ten percent HS produces a 1.4-fold increase in PPi production after 48 h of culture, while cartilage incubated in media containing 10% HP produces no more PPi than that incubated in media alone. PE stimulates a mean 2-fold increase in PPi production at 48 h in the presence of low concentrations of HP, and has no effect alone. It does not appear to up-regulate the activity of the ectoenzyme nucleoside triphosphate pyrophosphohydrolase (NTPPPH), nor does it promote the release of enzyme substrate into the extracellular space. Cartilage exposed to 0.5% HP and PE has 1.51 +/- 0.36 units of NTPPPH activity whereas cartilage exposed to 0.5% HP alone has 1.52 +/- 0.41 units of enzyme activity. PE does not increase the release of [14C]adenine-labeled compounds into the media. Approximately 13% of soluble 14C counts was found in the media of chondrocytes treated with PE while 18% of counts was released in the presence of HP alone. We have demonstrated a factor or factors present in FCS, HS, and an acid-ethanol extract of human platelets which represent(s) the first known physiologic modulators of PPi production in articular cartilage and may increase PPi production without affecting NTPPPH activity. 相似文献