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221.
Peptidyl transferase, the ribosomal enzyme which synthesizes peptide bonds, can catalyse the formation of ester linkages between α-hydroxyacyl-tRNA and aminoacyl-tRNA when ribosomes carry out a specific translation of phage R17 RNA in vitro. 相似文献
222.
Structure of the Purple Membrane 总被引:34,自引:0,他引:34
IN the preceding article1 it has been shown that a cell membrane fragment, the purple membrane, isolated from Halobacterium halobium2 contains retinal bound in a mole ratio of 1 : 1 to a protein of molecular weight 26,000 which is the only protein present. We now describe the structure of the purple membrane and its localization in the bacterial cell envelope. 相似文献
223.
224.
Virus Specific RNA in Cells transformed by RNA Tumour Viruses 总被引:21,自引:0,他引:21
Virus specific RNA comprises 5% of the nuclear RNA and 0.5–1.0% of the cytoplasmic RNA of cells transformed by murine sarcoma viruses. Even cryptically transformed cells which possess no detectable virus or viral proteins synthesize detectable amounts of viral RNA. 相似文献
225.
226.
Cell-free Studies on the Regulation of the Arabinose Operon 总被引:17,自引:0,他引:17
A DNA directed, cell-free system which synthesized L-ribulokinase coded by the L-arabinose operon ara OIBAD, has been developed. L-arabinose but not the araC gene product is required for the expression of this operon and, in addition, cyclic AMP and guanosine tetraphosphate are needed for optimal synthesis. 相似文献
227.
Inhibitors of the RNA and DNA Dependent Polymerase Activities of RNA Tumour Viruses 总被引:20,自引:0,他引:20
RNA viruses of several animal leukaemias and sarcomas possess what seems so far to be a unique enzyme—an RNA dependent DNA polymerase1–6. Specific inhibitors of the viral enzyme will not only be useful in the analysis of its possible role in neoplasia, but might provide drugs for leukaemia and cancer therapy. 相似文献
228.
Interactions between Marek's Disease Herpesvirus and Avian Leucosis Virus in Tissue Culture 总被引:3,自引:0,他引:3
A GROUP B herpesvirus is important in the aetiology of Marek's disease, a highly contagious lymphoproliferative disease of chickens1,2. Chicks inoculated with enveloped Marek's disease herpesvirus (MDHV), extracted from feather follicle epithelium of chickens with the disease, developed tumour-like aggregates of lymphoid cells in the viscera and frequently in the peripheral nerves3,4. Cultures of chicken embryo fibroblast (CEF) cells infected with MDHV develop discrete foci of altered cells5. Our data show that MDHV infection of cultures of CEF cells, previously infected with an avian leucosis virus (RAV-2), results in both a reduction in the number of MDHV foci and an increase in the complement fixing avian leucosis antigen (COFAL)6 titre. 相似文献
229.
ROBERT LAW 《Nature: New biology》1971,231(23):186-187
AIKEN and Vane have reported1 the independent actions of angiotensin I (AI) and angiotensin II (AII) on various isolated smooth muscle preparations, including rat colon. Tney showed that the apparent contractile action of AI on these preparations depended primarily on its in situ conversion to All by “converting enzyme” and that when the activity of the enzyme was inhibited by a pentapeptide extracted from Bothrops jararaca venom, the residual contractile action, probably due to unchanged AI, was very small. I have investigated the action of synthetic tetradecapeptide renin substrates (TPRS) on rat colon, in the light of the known actions of AI and All. 相似文献
230.