Naslov
Non-ribosomal synthesis of peptide products

Autori
Pavela-Vrančič, Maja ; Dieckmann, Ralf ; von Doehren, Hans

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Skup
40 godina molekularne biologije u Hrvatskoj

Mjesto i datum
Zagreb, Hrvatska, 1998

Vrsta sudjelovanja
Poster

Vrsta recenzije
Nije recenziran

Ključne riječi
peptide synthetases; tyrocidine synthetase; conformational changes; aminoacyl adenylation

Sažetak
Peptide synthetases constitute a family of multifunctional enzyme systems involved in the nonribosomal biosynthesis of a variety of microbial peptide products, some with important medical and biotechnological applications such as antibiotics (gramicidin S, tyrocidine, penicillins), immunomodulators (cyclosporin), extracellular surfactans (surfactin), and siderophores (enterobactin). The modular construction of the polypeptide chain opens the possibility for genetic manipulation by recombinational integration of alternative amino acid activating modules, and consequently generation of novel peptides with modified biological activity. Substrate activation is accomplished by formation of an acyladenylate, followed by charging of the activated moiety onto the sulfhydryl group of the enzyme bound 4˘-phosphopantetheine cofactor for subsequent modification and elongation. Peptide synthetase often do not display unique substrate specificity, as observed with aminoacyl-tRNA synthetases, allowing the synthesis of a variety of isoforms of their respective peptide product. Nevertheless, they may exhibit various degrees of selection providing highly conserved positions in the peptide structure. Discrimination control may take place at different levels of the overall process to ensure diversity of peptide structure. Tyrocidine synthetase 1 (TY1) was used as a suitable model system catalyzing the activation of one amino acid, L-Phe. A comparative analysis of the recombinant and wild type TY1 has shown that the overexpressed protein is divoid of the 4˘-phosphopantetheine cofactor. A significant difference in substrate recognition and binding affinity could not be established between the compared proteins, suggesting that the overall structure of the active site has not been affected. This produces an enzyme that can catalyze the first step of the reaction, whereby the overall process ceases with a tight bound adenylate in the active site. The acyladenylate may however react in a reverse reaction with MgPPi2- or is hydrolyzed by H2O. The presence of inorganic pyrophosphatase stops the reversal of the reaction, making it a suitable system for the analysis of aminoacyl adenylate stability in view of the putative proofreading system based on corrective hydrolysis on the aminoacyl adenylate level.

Izvorni jezik
Engleski

Znanstvena područja
Biologija

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