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1.
We have previously shown that replacing the P1-site residue (Ala) of chicken ovomucoid domain 3 (OMCHI3) with a Met or Lys results in the acquisition of inhibitory activity toward chymotrypsin or trypsin, respectively. However, the inhibitory activities thus induced are not strong. In the present study, we introduced additional amino acid replacements around the reactive site to try to make the P1-site mutants more effective inhibitors of chymotrypsin or trypsin. The amino acid replacement Asp-->Tyr at the P2' site of OMCHI3(P1Met) resulted in conversion to a 35000-fold more effective inhibitor of chymotrypsin with an inhibitor constant (K(i)) of 1. 17x10(-11) M. The K(i) value of OMCHI3(P1Met, P2'Ala) indicated that the effect on the interaction with chymotrypsin of removing a negative charge from the P2' site was greater than that of introducing an aromatic ring. Similarly, enhanced inhibition of trypsin was observed when the Asp-->Tyr replacement was introduced into the P2' site of OMCHI3(P1Lys). Two additional replacements, Asp-->Ala at the P4 site and Arg-->Ala at the P3' site, made the mutant a more effective inhibitor of trypsin with a K(i) value of 1. 44x10(-9) M. By contrast, Arg-->Ala replacement at the P3' site of OMCHI3(P1Met, P2'Tyr) resulted in a greatly reduced inhibition of chymotrypsin, and Asp-->Ala replacement at the P4 site produced only a small change when compared with a natural variant of OMCHI3. These results clearly indicate that not only the P1-site residue but also the characteristics, particularly the electrostatic properties, of the amino acid residues around the reactive site of the protease inhibitor determine the strength of its interactions with proteases. Furthermore, amino acids with different characteristics are required around the reactive site for strong inhibition of chymotrypsin and trypsin. 相似文献
2.
T Miura 《Plastic and reconstructive surgery》1979,63(2):242-244
A method for correction of an adduction contracture of the thumb is presented. Paired flaps provide good cover to the palmar and dorsal sides of the web space. This method produces better cosmetic and functional results than the traditional methods. 相似文献
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In poly(A)+RNA extracted from a lactating goat mammary gland, mRNA of about 750 nucleotides was shown to encode pre alpha-lactalbumin by using in vitro translation and immunoprecipitation. From the total poly(A)+RNA, the cDNA library was constructed using the Escherichia coli plasmid pUC18; it was screened with the oligodeoxyribonucleotide probe corresponding to the amino acid sequence of Trp60-Gln65 of goat alpha-lactalbumin. A plasmid containing almost full-length cDNA of goat pre alpha-lactalbumin, pGLA-1, was identified. The cDNA insert of pGLA-1 comprises 727 base pairs and contains the signal peptide and mature protein sequence. 相似文献
6.
Interleukin-1 derived from human monocytic leukemia cell line JOSK-I acts as an autocrine growth factor 总被引:1,自引:0,他引:1
Y Furukawa M Ohta Y Miura M Saito 《Biochemical and biophysical research communications》1987,147(1):39-46
Interleukin-1 (IL-1) enhances the growth of human monocytic leukemia cell line JOSK-I cells, which were recently established in our laboratory and which were demonstrated to produce a high level of IL-1 constitutively, in liquid as well as semisolid culture systems. Concomitantly, IL-1 stimulated the prostaglandin E2 synthesis and nitroblue tetrazolium dye-reducing capacity of JOSK-I cells. This indicates that IL-1 may act as autocrine growth factor for monocytes, and also suggests the possibility that this autocrine stimulation may play an important role in the pathophysiology of monocytic leukemia in vivo. 相似文献
7.
Effects of p-chloromercuribenzoate (PCMB) on the cytoskeletal organization of rat red blood cells were studied. Upon incubation with 50 microM PCMB in 10 mM Tris-HCl (pH 7.4) at 37 degrees C for 30 min, 80% of actin and 45% of spectrin were released from the ghosts, resulting in the fragmentation of ghost membranes. Addition of 2 mM Mg2+ or 0.1 M KCl, or lowering incubation temperature to 0 degree C substantially inhibited the solubilization of the cytoskeletal proteins and the fragmentation of ghost membranes, which enable to examine the effects of PCMB on the interaction between transmembrane proteins and the peripheral cytoskeletal network. Decreased recoveries of transmembrane proteins, such as band 3 and glycophorin, in Triton shell fraction were observed in the ghosts incubated with PCMB either in the presence of Mg2+ or at 0 degree C. PCMB also inhibited the in vitro association of purified spectrin with spectrin-depleted inside-out vesicles through interaction with proteins in the vesicle, such as bands 2.1 and 3. In the PCMB-treated ghosts, intramembrane particles were highly aggregated, which further supports the PCMB-induced dissociation of the transmembrane proteins from the cytoskeletal network. The decreased recovery of glycophorin in the Triton shell fraction also observed in intact red blood cells upon incubation with PCMB. These results suggest that the main action of PCMB on red cell membranes under physiological condition, at higher ionic strength and in the presence of Mg2+, is to dissociate transmembrane proteins from the peripheral cytoskeletal network, which may modify functions of these proteins. 相似文献
8.
Brefeldin A inhibits oligosaccharide processing of glycoproteins in mouse hypothyroid pituitary tissue at several subcellular sites 总被引:2,自引:0,他引:2
V S Perkel Y Miura J A Magner 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1989,190(3):286-293
We have studied the effects of brefeldin A (BFA) and monensin on the processing of the oligosaccharides of thyrotropin (TSH), free alpha-subunits, and cellular glycoproteins of mouse pituitary tissue to clarify the subcellular sites of action of BFA. BFA was previously shown to inhibit the translocation of glycoproteins from the rough endoplasmic reticulum to the Golgi apparatus but action at other sites was possible. Pituitaries from hypothyroid mice were incubated with [35S]methionine, [3H]mannose, [3H]galactose, [3H]fucose, N-[3H]acetylmannosamine, or [35S]sulfate for 2 hr in the absence or presence of 5 micrograms of BFA/ml or 2 microM monensin. TSH and free alpha-subunits were immunoprecipitated from tissue lysates and analyzed by sodium dodecyl sulfate-gel electrophoresis. The tryptic glycopeptides of TSH were separated using high-performance liquid chromatography. Total glycoproteins in cell lysates were precipitated using trichloroacetic acid. Labeled oligosaccharides were released from the tryptic glycopeptides of TSH and cellular glycoproteins by endoglycosidase H and they were analyzed by paper chromatography. Compared with control incubations, BFA caused the intracellular accumulation of glycoproteins having less than expected amounts of Man9GlcNAc2 units, but with excess Man8GlcNAc2, Man7GlcNAc2, Man6GlcNAc2, and Man5GlcNAc2 units. There was a lesser accumulation of glucose-containing oligosaccharides, especially Glc1Man9GlcNAc2. Monensin also caused the accumulation of certain high mannose species, but the pattern differed from that seen for BFA, since Man9GlcNAc2 units were preserved and there was less excess of Man8GlcNAc2, Man7GlcNAc2, Man6GlcNAc2, and Man5GlcNAc2 units. BFA did not block the initial attachment of oligosaccharides at any of the three Asn-glycosylation sites of TSH, but caused the accumulation of Man5-8GlcNAc2 units at each site. Both monensin and BFA inhibited fucosylation, sulfation, and sialylation more markedly than mannose incorporation. Thus, in addition to its previously described action of inhibiting rough endoplasmic reticulum to Golgi transport, BFA appears to partially inhibit the glucose-trimming enzymes as well as some Golgi enzymes. 相似文献
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10.
Purification and characterization of two serine isoacceptor tRNAs from bovine mitochondria by using a hybridization assay method. 总被引:8,自引:8,他引:0
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For large scale preparation of mitochondrial tRNAs, a new hybridization assay method using synthetic oligodeoxyribonucleotide probes (16-17mer) complementary to individual tRNA sequences was developed and applied for the purification of two serine isoacceptor tRNAs (tRNASerAGY and tRNASerUCN) from bovine mitochondria. It is about 100 times more sensitive than the conventional aminoacylation assay method. 2-4 A260 units each of both tRNASer isoacceptors were purified from 17.5 kg of bovine liver, and they were characterized by means of nuclease digestion, melting profiles and aminoacylation activity. It is suggested that tRNASerUCN possesses the D loop/T loop interaction like usual L-shaped tRNAs, and that tRNASerAGY lacking almost an entire D arm is aminoacylated with an efficiency not very much lower than that of tRNASerUCN. 相似文献