Peptide-carrier protein

Wang TT, Fellows PF, Leighton TJ et al (2004) Induction of opsonic antibodies to the gamma-D-glutamic acid capsule of Bacillus anthracis by immunization with a synthetic peptide-carrier protein conjugate. FEMS Immunol Med Microbiol 40 231-237... 

Coupling reagent Peptide Carrier protein Binding to ... 

Figure 6 HMGS containing biosynthetic pathways. Portions of the PKS and PKS/NRPS pathways where the HMGS and related enzymes are located. Abbreviations A - Adenylation, AGP - acyl carrier protein, AT - acyltransferase, Cy - cyciization, DH - dehydratase, ER - enoyl reductase, GNAT -CCN5-related N-acetyltransferase, KS - ketosynthase, KR - ketoreductase, MT - methyltransferase. Ox - Oxidase, Oxy - Oxygenase, PGP - peptide carrier protein, PhyH - phytanoyl-CoA dioxygenase, PS - pyrone synthase, TE - thioesterase, - unknown function, - inactive domain.

Specific labeling can also be accomplished through the targeting of specific protein domains. In one report, an 80 amino acid peptide carrier protein (PCP) domain derived from a nonribosomal peptide synthetase was fused to a protein of interest [72]. After expression and lysis of the cells, biotinylated derivative 44 was installed on this domain by an added phosphopantetheinyl transferase,... 

ACP Acyl carrier protein PCP Peptide carrier protein... 

Because the nature of the bond fonnalion process is different in PKs and NRPs (Claisen condensations vs. peptide bond formalion), NRPSs necessarily utilize different domains. Specifically, the three essential domains of the NRPS are an adenylation (A), peptide carrier protein (PCP), and condensation (C) domain. NRP biosynthesis begins with activation of the amino add through adenylation of the carboxylic acid group by the A domain, a process facilitated by the presence of Mg +. In the adenylation reaction, ATP reacts with the selected amino acid to form the activated phosphoester aminoacyl adenylate and pyrophosphate (Figure 4.10a). The A domain is also a key point of selectivity during NRP biosynthesis as it is responsible for the selection of the particular amino acid to be activated. 

An amino acid (Scheme 12.74) such as isoleucine (He, I) is adenylated and is then attached to the peptide carrier protein (PCP) through a sulfur linkage (4-phosphopantetheine) as shown in the block diagram of Scheme 12.73. A second... 

Another approach comes from Professor Christopher T. Walsh s laboratory at Harvard Medical School. The Walsh laboratory studies the biosynthesis of natural products (natural products are small molecules created by nature). What does natural product biosynthesis have to do with cellular imaging Like the AGT method where a DNA repair protein is used, it turns out that some of the proteins involved in natural product assembly are useful for labeling the cell surface. Peptide carrier proteins (PCPs) are 80- to 120-amino acid domains of nonribosom peptide synthetases (NRPSs). NRPSs are protein megacomplexes used by many microbial species, like Pseudomonas and Streptomyces, to biosynthesize natural products from common amino acid precursors. An enzyme called a phosphop-antetheinyl transferase will covalently attach the 4 -phosphopantethei-nyl moiety of coenzyme A to a specific serine residue in the PCP domain. One phosphopantetheinyl transferase, Sfp from a microbe... 

Fig. 3. Processing steps of rat and bovine prepro-vasopressin lea ding to the hormone vasopressin and its carrier protein, neurophysin (14). (a) Putative signal peptide (b) vasopressin (c) neurophysin (d) glycopeptide. CHO = carbohydrate.

All the aforementioned advantages and several additional features apply to ELP-based macromolecular carriers. First, ELP-based carriers are thermally responsive. Second, ELP is a biopolymer and therefore is nontoxic and biodegradable. Third, the gene-based synthesis of ELP allows the creation of genetic fusions with functional peptides and proteins, such as targeting sequences. 

Micellar nanocarriers have already been applied successfully for delivery of hydro-phobic drugs [86]. These carriers are usually the product of self-assembled block copolymers, consisting of a hydrophilic block and a hydrophobic block. Generally, an ELP with a transition temperature below body temperature is used as hydrophobic block and the hydrophilic block can be an ELP with a transition temperature above body temperature or another peptide or protein. The EPR effect also directs these types of carriers towards tumor tissue. 

D. T. O Hagan and L. Ilium, Absorption of peptides and proteins from the respiratory tract and the potential for development of locally administered vaccine, Crit. Rev. Ther. Drug Carrier Syst, 7, 35-97 (1990). 

Atherton E, Logan CJ, Sheppard RC, Peptide synthesis, part 2 Procedures for solid phase synthesis using W-lluorcnylmcthoxycarbon-ylamino acids on polyamide supports Synthesis of substance P and of acyl carrier protein 64—74 decapeptide. J Chem Soc Perkin Trans 1 1981 ... 

VHL Lee, A Yamamoto, U Kompella. (1991). Mucosal penetration enhancers for facilitation of peptide and protein drug absorption. CRC Crit Rev Drug Carrier Sys 8 91-192. 

Figure 11.5 Amino acid building blocks are incorporated into daptomycin backbone successively by NRPS subunits DptA, DptBC and DptD (a). Structural diversity of daptomycin peptide core can be obtained by genetic modifications of dpt gene cluster (b). C, condensation domain A, adenylation domain PCP, peptidyl carrier protein E, epimerase TE, thioesterase domain... 

In another study, the carrier protein was replaced by an enzyme compatible solid-phase resin (PEGA), and enzyme-catalyzed cyclization was used to probe substrate specificity. This study demonstrated also that oxo-esters are tolerated as substrates for TE domains, and then-preparation in library format served as an excellent tool for substrate specificity studies, as well as for preparation of cyclized peptides. Figure 13.11 shows how the TycA TE showed selectivity for only residues 1 and 9 (colored in red), and changes at all other residues were tolerated [42]. Hydrogen bonding interactions are shown in green. Several compounds made from this series were shown to demonstrate improved therapeutic indices (with respect to hemolysis) while retaining antimicrobial activity. 

During the past 10 years, one of the most exciting developments in the oral peptide drug delivery was the identification of PEPT1. This is a significant finding because this carrier protein is known to play a critical role in the absorption of... 

Hydrophilic peptides and proteins are frequently large molecules they may enter the brain by carrier-mediated transport, receptor-mediated transcytosis, or by adsorptive-mediated transcytosis. Small peptides, such as di- and tripeptides are transported by the specific transporters, PepTl and PepT2, but neither of them is present at the BBB. Nevertheless, there is saturable brain uptake of the tripeptide glutathione and of several opioid peptides, suggesting that specific transporters, as... 

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