Prokaryotic expression of streptolysin O antigen and its condition optimization / 国际检验医学杂志

Objective To construct the recombinant streptolysin O antigen(SLO) prokaryotic expression plasmid and establish its best expression condition in Escherichia coli .Methods The DNA fragment encoding SLO was amplified from streptococcal ge-nomic DNA template by PCR ,and then incorporated into pET-32a(+ ) vector to construct pET-32a(+ )-SLO recombinant plas-mid .pET-32a(+ )-SLO was transformed into Escherichia coli BL21(DE3) and SLO protein was expressed and purified by isopro-pyl-β-D-thiogalactoside(IPTG)-induction and auto-induction ,respectively .Results The results of DNA electrophoresis and DNA sequencing showed that pET-32a(+ )-SLO recombinant plasmid was constructed successfully .When IPTG at different concentra-tion was used ,SLO expressed as inclusion body and its expression efficiency was low .Under auto-induction condition ,SLO ex-pressed as partly soluble manner ,and its expression efficiency increased .Conclusion The prokaryotic expression plasmid pET-32a (+ )-SLO is constructed successfully and the best condition for SLO expression and purification from Escherichia coli culture is es-tablished ,which lay the foundation for further basic and clinical application research with SLO .

Construction of HPV18E7 recombinant plasmid and exploration of its optimization expression condition in Escherichia coli / 重庆医学

Objective To construct recombinant plasmids containing HPV18E7 gene ,and explore the optimization condition of its expression in Escherichia coli .Methods The genomic DNA extracted from HeLa cell line which served as a template to the HPV18 E7 gene was amplified using PCR method ;and the amplified product of HPV18E7 gene was connected to the pET-32a(+ ) vector ,which composed the pET-32a(+ )-HPV18E7 recombinant plasmid ;the positive recombinant plasmids were transformed into BL21-DE3-pLysS competent cells and the optimized expression condition was explored in order to obtain a large amount of HPV18E7 oncogenic protein .Results The fragment length of PCR products of HeLa cell genomic DNA was consistent with that of HPV18 E7 gene .In LB medium ,the expression level of the target protein was not high under such conditions as different concentra-tion of IPTG and lactose ,different temperatures and different induction starting amount .Therefore the ZYM-5052 auto-induction medium was tried in this experiment ,and the expression amount of the fusion protein was much higher than that induced with IPTG and lactose .Conclusion The amount of HPV18E7 fusion protein in ZYM-5052 automatic induction medium is much higher than that induced with IPTG and lactose .

Quorum sensing (QS) as etiological phenomenon: the bacterial paradigm.

Signaling mechanisms that govern physiological and morphological responses to change the cell density are common in bacteria. Quorum sensing is signal transduction processes which involves the production and release of and response to hormone-like molecules (auto-inducers) that accumulate in the external environment as the cell population grows. Quorum sensing is found in a wide variety of bacteria, both Gram-positive and Gram-negative and the spectrum of physiological functions that can be regulated is impressive. Variation in the nature of the extra-cellular signal in the signal detection machinery and in the mechanisms of signal transmission demonstrates the evolutionary adaptability of quorum sensing systems for multiple uses.