Peptides

The nuclear transcription factor NF-kappaB up regulates gene expression during inflammation and has critical roles in carcinogenesis, anti-apoptosis, invasion, and metastasis. This has led to the search for specific inhibitors of NF-kappaB to help study NF-kappaB for possible treatments for inflammatory diseases and cancer in the future.NF-kappaB is held in an inactive state in the cytoplasm as a heterodimer containing a p65 subunit. Signalling leads to revealing of a hidden nuclear localisation sequence within p65, phosphorylation of p65, and translocation to the nucleus. p65 binds to DNA and ultimately transcription of specific genes. Therefore, finding an inhibitor of the nuclear localisation sequence and phosphorylation of the p65 subunit is an attractive target.A peptide named PTD-p65-P1 was generated from the p65 DNA binding domain mimicking the phosphorylated state, attached to a membrane-translocating peptide sequence generated from antennapedia (PTD). PTD-p65-P1 has been shown to inhibit NF-kappaB binding to DNA in a dose dependent manner. This activity was also known to be specific for NF-kappaB inhibition. The inhibition of NF-kappaB activity by PTD p65-P1 was shown to be effective against a range of stimuli including cigarette smoke, interleukin 1 and hydrogen peroxide which suggests the inhibitor acts on a common step against these stimuli. The presence of PTD p65-P1 inhibits the cytoplasmic p65 subunit phosphorylation or translocation. The reporter genes tested for NF-kappaB activity showed down regulation of gene expression in the presence of PTD-p65-P1 peptide. The evidence is compelling that this peptide could be a suitable model for a selective specific inhibitor of NF-kappaB activity for therapeutic use in the future.

Substrate peptide for C-terminal Src kinase (Csk) for use in kinase assays. Csk is a cytosolic tyrosine kinase that is closely related to the kinase Src and is a well-known negative regulator of Src family kinases. Csk has both tumour suppressor and oncogenic properties and has also been implicated in regulating blood pressure, making Csk a novel therapeutic target for hypertension disorders.

The identification of T cell epitopes is vital for a range of immunological functions including viral vaccine design. Current influenza vaccines are designed to induce protective humoral immunity by exposure to inactivated influenza leading to an induction of potent CD4+ T cell memory.  However, little is known about how these primed CD4+ T cells effect the response to other viruses that share a common T cell epitope.Sendai Virus nucleoprotein (324-332) has been identified as a T cell epitope and used in T cell assays to stimulate a response. Further use of Sendai virus nucleoprotein (324-332) epitope in vitro could help uncover the effect of immune response to heterologous viruses with common epitopes. It may also help understand the impact of using primed CD4+ T cell as vaccines. This could have consequences for future vaccine design to improve specificity and potency of the immune cells.

Histone 4 (H4) is one of the four core histones (H2A, H2B, H3 and H4) which are essential for compacting eukaryotic DNA into the nucleosome. Due to the high lysine and arginine content, histones have a net positive charge and therefore electrostatically interact with negatively charged DNA. The nucleosome arises when 147 base pairs of DNA wrap around a H3-H4 tetramer and two H2A-H2B dimers, forming the histone octamer core. Like other core histones, H4 has a globular domain and a flexible N-terminal domain, the histone tail, which can undergo modifications such as acetylation, methylation, phosphorylation and ubiquitination.Gene transcriptional activation or inactivation is controlled by ATP-dependent chromatin remodelling factors and histone modifying enzymes. Both processes function to alter the positioning of the nucleosome, allowing the DNA within to be either accessible to the transcription machinery or inaccessible. H4 lysine rich tail plays a role in the higher order chromatin folding.The lysine at position 16 has been acetylated, which neutralizes the positive charge on the amino acid, loosening the chromatin structure. This alteration to the accessibility of chromatin promotes the initiation of transcription.Acetyl-Histone H4 (1-23) K16Ac-GG-[Lys(5-FAM)] has a C-terminal GGK linker labelled with 5-Carboxyfluorescein (5-FAM), a widely used green fluorescent tag. Additionally, this peptide has an uncharged C-terminal amide and is protected from N-terminal modifications by a covalently bonded acetyl group.

Cecropins are a lytic peptide family, originally isolated from Hyalophora cecropia. Cecropin-B is a cationic helical peptide that can form pores, this is believed to be the reason for its such potent lytic activity. Cecropin-B has been shown to be effective against both Gram-positive and Gram-negative bacteria plus numerous cancer cell lines including multidrug-resistant types. The ability to insert into the cell membrane and lead to pore formation is attributed to the amphipathic groups present creating amphipathic regions. The effectiveness of cecropin-B on cancer cells has led to further use of the peptide as a model for potential new anticancer drugs including cyclic cationic forms.