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761.
A method was devised to produce antibodies to lipopolysaccharide (LPS) in guinea-pigs following a single immunization. The antigen was prepared by mixing polymyxin B-agarose with LPS from Escherichia coli O55:B5. Use of the agarose support allowed purification of the complex by simple washing procedures. Twenty-nine days after a single injection of the immunogen mixed with Freund complete adjuvant all animals demonstrated antibody to the LPS portion of the complex. No antibodies were detected to the polymyxin B component. Typical titres of LPS as measured by ELISA were 2(11). After, a booster immunization, titres of LPS antibody were further increased and a greater avidity was noted. In contrast to other methods which have been employed for production of antibody to LPS, use of the polymyxin B-agarose complex has the following advantages: ease of antigen preparation, ready purification of the complex, potent immunostimulation, and under the conditions employed here, LPS-specific antibody production, without accompanying antibody to polymyxin B. 相似文献
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Initiation factors of protein biosynthesis in bacteria and their structural relationship to elongation and termination factors 总被引:7,自引:0,他引:7
Initiation of protein biosynthesis in bacteria requires three initiation factors: initiation factor 1, initiation factor 2 and initiation factor 3. The mechanism by which initiation factors form the 70S initiation complex with initiator fMet-tRNAfMet interacting with the initiation codon in the ribosomal P site and the second mRNA codon exposed in the A site is not yet understood. Here, we present a model for the function of initiation factors 1 and 2 that is based on the analysis of sequence homologies, biochemical evidence and the present knowledge of the three-dimensional structures of translation factors and ribosomes. The model predicts that initiation factors 1 and 2 interact with the ribosomal A site mimicking the structure of the elongation factor G. We present data that extend the mimicry hypothesis to initiation factors 1 and 2, originally postulated for the aminoacyl-tRNA·elongation factor Tu·GTP ternary complex, elongation factor G and release factors. 相似文献
764.
Yeast hnRNP K-Like Genes Are Involved in Regulation of the Telomeric Position Effect and Telomere Length 下载免费PDF全文
Mammalian heterogeneous nuclear ribonucleoprotein K (hnRNP K) is an RNA- and DNA-binding protein implicated in the regulation of gene expression processes. To better understand its function, we studied two Saccharomyces cerevisiae homologues of the human hnRNP K, PBP2 and HEK2 (heterogeneous nuclear RNP K-like gene). pbp2Delta and hek2Delta mutations inhibited expression of a marker gene that was inserted near telomere but not at internal chromosomal locations. The telomere proximal to the ectopic marker gene became longer, while most of the other telomeres were not altered in the double mutant cells. We provide evidence that telomere elongation might be the primary event that causes enhanced silencing of an adjacent reporter gene. The telomere lengthening could, in part, be explained by the inhibitory effect of hek2Delta mutation on the telomeric rapid deletion pathway. Hek2p was detected in a complex with chromosome regions proximal to the affected telomere, suggesting a direct involvement of this protein in telomere maintenance. These results identify a role for hnRNP K-like genes in the structural and functional organization of telomeric chromatin in yeast. 相似文献
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