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61.
62.
Actinomycins II and III, containing sarcosine residues in two adjacent sites of their peptide moieties were produced by Streptomyces antibioticus in the presence of exogenous sarcosine labeled with deuterium in the N-methyl group. Combined gas chromatography-mass spectrometry of the cyclodipeptides derived by thermal degradation of these actinomycins demonstrated specific incorporation of the labeled sarcosine into the 3-site, implicating some other biosynthetic precursor, presumably glycine, for the sarcosine in the 4-site. The same conclusion emerged from proton nuclear magnetic resonance spectroscopy of these deuterium-labeled actinomycins. 相似文献
63.
The activities of cAMP-dependent and independent protein kinases were determined after feeding confluent glioma C6-BU-1 cultures. It has been shown that the activity of both enzymes rose considerably after feeding, and that the ratio of 32P incorporation into histone, in the absence and the presence of cAMP, was maximal 4 hours after feeding. This increase in protein kinase activity was followed by the activation of ornithine decarboxylase and accumulation of putrescine. Spermine, at millimolar concentrations, inhibited protein kinase, apparently by inactivating the catalytic subunit. It is suggested that this inhibition of protein kinase by polyamines is another regulatory mechanism, which controls cellular growth. 相似文献
64.
Studies on the biological activities of actinomycins Z1 and Z5 总被引:1,自引:0,他引:1
The biological activities of actinomycins Z1, Z5, and IV (D) were compared. No consistent pattern was observed between the in vitro and in vivo results. Inhibition of E. coli DNA-dependent RNA polymerase in vitro followed the sequence IV > Z1 > Z5; however, for inhibition of RNA synthesis in B. subtilis and in HeLa cells the sequence was IV > Z5 > Z1 and the latter relationship was seen in the antimicrobial activity also. Physicochemical data did not agree with any of these findings. Difference spectra obtained with B. subtilis and M. lysodeikticus DNA followed the sequence Z1 > IV > Z5, while the relative thermal denaturation profiles were the exact opposite, Z5 > IV > Z1. These physicochemical criteria appear to be less reliable quantitative guides to biological activity. The relative ineffectiveness of actinomycin Z1in vivo is probably the result of permeability differences associated with the presence of an hydroxylated proline residue (3-hydroxy-4-oxo-5-methylproline). 相似文献
65.
ATP-dependent oxalate facilitated calcium transport in sarcoplasmic reticulum (SR) preparations obtained from rabbit vastus lateralis muscle (fast skeletal muscle; Fsr) and soleus (slow skeletal muscle; Ssr) was determined. Addition of exogenous calmodulin did not stimulate calcium transport in either Fsr or Ssr preparations. Fsr and Ssr previously washed in 1 mM EGTA demonstrated a reduced capacity to transport Ca2+; the exogenous addition of calmodulin (0.24 μM) under these conditions, did not restore uptake activity but significantly decreased the steady-state level of Ca2+ uptake. Extracts of skeletal SR prepared by treatment with 0.2 mM EDTA and boiling produced significantly more stimulation of red cell Ca2+ATPase activity than extracts prepared by boiling alone. This stimulation of red cell Ca2+-ATPase was inhibited to a significant extent by , a known anti-calmodulin agent. Radioimmunoassay revealed that extracts prepared by boiling or EDTA-treatment followed by boiling contained considerable amounts of calmodulin. Washing with 1 mM EGTA, though, did not release any calmodulin from SR. These studies reveal that calmodulin is present in both Fsr and Ssr and can only be removed by harsh treatments. The role of calmodulin in skeletal muscle Ca2+-transport remains to be determined. 相似文献
66.
67.
Background
One of the major challenges in post-genomic era is to provide functional annotations for large number of proteins arising from genome sequencing projects. The function of many proteins depends on their interaction with small molecules or ligands. ATP is one such important ligand that plays critical role as a coenzyme in the functionality of many proteins. There is a need to develop method for identifying ATP interacting residues in a ATP binding proteins (ABPs), in order to understand mechanism of protein-ligands interaction. 相似文献68.
69.
70.
The signal produced by fluorescence in situ hybridization (FISH) often is inconsistent among cells and sensitivity is low. Small DNA targets on the chromatin are difficult to detect. We report here an improved nick translation procedure for Texas red and Alexa Fluor 488 direct labeling of FISH probes. Brighter probes can be obtained by adding excess DNA polymerase I. Using such probes, a 30 kb yeast transgene, and the rp1, rp3 and zein multigene clusters were clearly detected. 相似文献