The folding of many newly synthesized proteins in the cell depends on a set of conserved proteins known as molecular chaperones. These prevent the formation of misfolded protein structures, both under normal conditions and when cells are exposed to stresses such as high temperature. Significant progress has been made in the understanding of the ATP-dependent mechanisms used by the Hsp70 and chaperonin families of molecular chaperones, which can cooperate to assist in folding new polypeptide chains.

Molecular chaperones in cellular protein folding.

https://www.cell.com/cell/pdf/S0092-8674(00)80787-4.pdf

Polypeptide flux through bacterial Hsp70: DnaK cooperates with trigger factor in chaperoning nascent chains.

http://wolfson.huji.ac.il/expression/local/febs-1999.pdf

Synonymous codon substitutions affect ribosome traffic and protein folding during in vitro translation

http://www.jbc.org/content/272/52/32715.full.pdf

Cotranslational Protein Folding

Recent advances in producing and selecting functional proteins by using cell-free translation

In this paper, an attempt has been made to design a low-cost noncontact capacitance-type level sensor for a conducting liquid. The sensor is in the form of a uniform circular cylinder made of insulating material like glass, ceramic, plastic, etc. The sensor is connected with the metallic- or nonmetallic-type liquid storage tank, in which the conducting liquid column is taken as one electrode, and a noninductively wound short-circuited outside coil is taken as the other electrode of a variable capacitor. The change in capacitance due to the change of liquid level is measured by a modified linear operational-amplifier-based De' Sauty bridge network with adjustable bridge sensitivity. The bridge output after amplification and rectification may be used to drive a direct current indicator calibrated in level. The studies have been made with high-density polyethylene and glass tube sensors separately in both metallic and nonmetallic storage tanks with tap water as the conducting liquid, and the experimental results of the static characteristics of the level sensors with percentage error from linearity are presented in the paper. These results are found to have good linearity and repeatability within acceptable limits

A low-cost noncontact capacitance-type level transducer for a conducting liquid

Ribosomes from a number of prokaryotic and eukaryotic sources (e.g., Escherichia coli, wheat germ and rat liver) can refold a number of enzymes which are denatured with guanidine/HCl prior to incubation with ribosomes. In this report, we present our observations on the refolding of denatured lactate dehydro-genase from rabbit muscle and glucose-6-phosphate dehydrogenase from baker's yeast by ribosomes from E. coli, wheat germ and rat liver, The protein-folding activity of E. coli, ribosomes was found to be present in 50s particles and in 23S rRNA. The 30S particle or 16S rRNA did not show any protein-folding activity. The protein-folding activity of 23S rRNA may depend on its tertiary conformation. Loss of tertiary structure, by incubation with low concentrations of EDTA, inhibited the protein-folding activity of 23S rRNA. This low concentration of EDTA had no effect on folding of the denatured enzymes by themselves.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1996.00613.x

In vitro protein folding by ribosomes from Escherichia coli, wheat germ and rat liver: the role of the 50S particle and its 23S rRNA

Breast cancer is considered as an increasing major life-threatening concern among the malignancies encountered globally in females. Traditional therapy is far from satisfactory due to drug resistance and various side effects, thus a search for complementary/alternative medicines from natural sources with lesser side effects is being emphasized. Andrographis paniculata, an oriental, traditional medicinal herb commonly available in Asian countries, has a long history of treating a variety of diseases, such as respiratory infection, fever, bacterial dysentery, diarrhea, inflammation etc. Extracts of this plant showed a wide spectrum of therapeutic effects, such as anti-bacterial, anti-malarial, anti-viral and anti-carcinogenic properties. Andrographolide, a diterpenoid lactone, is the major active component of this plant. This study reports on andrographolide induced apoptosis and its possible mechanism in highly proliferative, invasive breast cancer cells, MDA-MB-231 lacking a functional p53 and estrogen receptor (ER). Furthermore, the pharmacokinetic properties of andrographolide have also been studied in mice following intravenous and oral administration. Andrographolide showed a time- and concentration- dependent inhibitory effect on MDA-MB-231 breast cancer cell proliferation, but the treatment did not affect normal breast epithelial cells, MCF-10A (>80 %). The number of cells in S as well as G2/M phase was increased after 36 h of treatment. Elevated reactive oxygen species (ROS) production with concomitant decrease in Mitochondrial Membrane Potential (MMP) and externalization of phosphatidyl serine were observed. Flow cytometry with Annexin V revealed that the population of apoptotic cells increased with prolonged exposure to andrographolide. Activation of caspase-3 and caspase-9 were also noted. Bax and Apaf-1 expression were notably increased with decreased Bcl-2 and Bcl-xL expression in andrographolide-treated cells. Pharmacokinetic study with andrographolide showed the bioavailability of 9.27 ± 1.69 % with a Cmax, of 0.73 ± 0.17 μmol/L and Tmax of 0.42 ± 0.14 h following oral administration. AG showed rapid clearance and moderate terminal half lives (T1/2) of 1.86 ± 0.21 and 3.30 ± 0.35 h following IV and oral administration respectively. This investigation indicates that andrographolide might be useful as a possible chemopreventive/chemotherapeutic agent for human breast cancers.

https://link.springer.com/content/pdf/10.1186%2Fs12929-016-0257-0.pdf

Cytotoxicity and cell cycle arrest induced by andrographolide lead to programmed cell death of MDA-MB-231 breast cancer cell line.

The radioprotective activity of Piper betel ethanolic extract (PE) has been studied using rat liver mitochondria and pBR 322 plasmid DNA as two model in vitro systems. The extract effectively prevented gamma-ray induced lipid peroxidation as assessed by measuring thiobarbituric acid reactive substrates, lipid hydroperoxide and conjugated diene. Likewise, it prevented radiation-induced DNA strand breaks in a concentration dependent manner. The radioprotective activity of PE could be attributed to its hydroxyl and superoxide radicals scavenging property along with its lymphoproliferative activity. The radical scavenging capacity of PE was primarily due to its constituent phenolics, which were isolated and identified as chevibetol and allyl pyrocatechol.

/pdf/radioprotective-property-of-the-ethanolic-extract-of-piper-1fhd5h67px.pdf

Radioprotective Property of the Ethanolic Extract of Piper betel Leaf

Escherichia coli ribosome, its 50S subunit, or simply the 23S rRNA can reactivate denatured proteins in vitro. Here we show that protein synthesis inhibitors chloramphenicol and erythromycin, which bind to domain V of 23S rRNA of E. coli, can inhibit reactivation of denatured pig muscle lactate dehydrogenase and fungal glucose-6-phosphate dehydrogenase by 23S rRNA completely. Oligodeoxynucleotides complementary to two regions within domain V (which cover sites of chloramphenicol resistant mutations and the putative A site of the incoming aminoacyl tRNA), but not to a region outside of domain V, also can inhibit the activity. Domain V of 23S rRNA, therefore, appears to play a crucial role in reactivation of denatured proteins.

Subrata Chattopadhyay

Papers

A low-cost noncontact capacitance-type level transducer for a conducting liquid

In vitro protein folding by ribosomes from Escherichia coli, wheat germ and rat liver: the role of the 50S particle and its 23S rRNA

Cytotoxicity and cell cycle arrest induced by andrographolide lead to programmed cell death of MDA-MB-231 breast cancer cell line.

Radioprotective Property of the Ethanolic Extract of Piper betel Leaf

Reactivation of denatured proteins by 23S ribosomal RNA: role of domain V.