nested-splicing by overlap extension PCR improves specificity of this standard method

Background: splicing by overlap extension [SOE] PCR is used to create mutation in the coding sequence of an enzyme in order to study the role of specific residues in protein's structure and function

Objectives: we introduced a nested-SOE-PCR [N -SOE-PCR] in order to increase the specificity and generating mutations in a gene by SOE-PCR

Materials and Methods: genomic DNA from Bacillus thermocatenulatus was extracted. Nested PCR was used to amplify B. thermocatenulatus lipase gene variants, namely wild type and mutant, using gene specific and mutagenic specific primers, followed by cloning in a suitable vector. Briefly in N-SOE-PCR method, instead of two pairs of primers, three pairs of primers are used to amplify a mutagenic fragment. Moreover, the first and second PCR products are slightly longer than PCR products in a conventional SOE. PCR products obtained from the first round of PCR are used for the second PCR by applying the nested and mutated primers. Following to the purification of the amplified fragments, they will be subject of the further purification and will be used as template to perform the third round of PCR using gene specific primers. In the end, the products will be cloned into a suitable vector for subsequent application

Results: in comparison to the conventional SOE-PCR, the improved method [i.e. N-SOE-PCR] increases the yield and specificity of the products. In addition, the proposed method shows a large reduction in the non-specific products

Conclusions: by applying two more primers in the conventional SOE, the specificity of the method will be improved. This would be in part due to annealing of the primers further inside the amplicon that increases both the efficiency and a better attachment of the primers. Positioning of the primer far from both ends of an amplicon leads to an enhanced binding as well as increased affinity in the third round of amplification in SOE

Periplasmic expression of Bacillus thermocatenulatus lipase in Escherichia coli in presence of different signal sequences

Efforts to express lipase in the periplasmic space of Escherichia coli have so far been unsuccessful and most of the expressed recombinant lipases accumulate in the insoluble cell fraction. To evaluate the role of native and heterologous signal peptides in translocation of the lipase across the inner membrane of E. coli, the lipase gene [btl2] was cloned downstream of the native Bacillus signal peptide and also in fusion with the pelB, ansB and ansB/asp signal peptides. For this purpose, four recombinant expression vectors [pYRKP.P, pYRKP.N, pYRKP. A and pYRKP.AA] were constructed and expressed in E. coli. Osmotic shock analysis showed that recombinant lipase was overexpressed as inclusion bodies in E. coli. The lipase inclusion bodies were subsequently solublized, refolded and purified using single column ion-exchange chromatography. To evaluate localization of lipase in the cell, the purified lipases were subjected to capillary isoelectric focusing and tandem mass spectrometry. Results showed that all signal peptides were able to direct the lipase from the cytoplasm into the periplasmic space of E. coli, because the periplasmic space of E. coli is not suitable for lipase folding, the translocated lipase aggregates in this space as inclusion bodies

Plasma myeloperoxidase activity and apolipoprotein A-1 expression in chronic hepatitis B patients

Hepatitis B virus initiates a complicated cascade process leading to chronic hepatitis B, cirrhosis, and hepatocellular carcinoma. In inflammatory situations, myeloperoxidase is released in plasma and binds to apolipoprotein A-1 in high-density lipoproteins. This study aims to evaluate the level of plasma myeloperoxidase as well as the pattern of plasma proteins in patients with chronic hepatitis B. Included in this study were 30 male subjects: 19 chronic hepatitis B patients, 6 HBV-related cirrhotic patients, and 5 healthy controls. Plasma myeloperoxidase was measured using enzyme-linked immunosorbent assay. Proteomic analysis of plasma proteins was performed by two-dimensional gel electrophoresis [2-DE] and mass spectrometry. One way ANOVAwas used for data analysis. Mean plasma myeloperoxidase levels were higher in patients with liver cirrhosis [65.5 +/- 12.5; P=0.007] and chronic hepatitis B [53.7 +/- 10.6; P=0.18] when compared with healthy subjects [45 +/- 7.6]. Moreover, a positive correlation was found between plasma myeloperoxidase levels and hepatic fibrosis stage [r=0.53, P=0.002; r=0.63, P=0.000]. Proteomic analysis showed an altered plasma protein pattern in progressive hepatitis B and down-regulation of the major apolipoprotein A-1 along with the appearance of a variety of spots noted to be apolipoprotein A-1isoforms with different molecular masses. In this study, progressive liver injury due to HBV infection correlated with higher plasma myeloperoxidase and an altered plasma apolipoprotein A-1 pattern