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Heteromeric endolysins encoded in a single gene: occurrence in Gram-positive targeting phages and relevance for lytic activity
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Resumo(s)
Antibiotic resistance is one of the major threats of our time, which has been driving research on antibacterial alternatives. Among these are endolysins, enzymes that digest the peptidoglycan, the major and essential constituent of the bacterial cell wall. Endolysins are produced by bacteriophages, the viruses that infect bacteria, which use them to lyse host cells at the end of the viral replicative cycle for virion progeny release. Those that target Gram-positive bacteria have a typical modular architecture, with one or more catalytic domains responsible for peptidoglycan cleavage in the N-terminal region, and a C-terminal module carrying one or more motifs involved in cell wall binding. Although generally monomeric, two-subunit heteromeric endolysins have already been described. For the recently discovered examples, it was found that the two subunits are produced from a single gene, thanks to the presence of an internal translation start site (ITSS) that allows translation of a smaller reading frame into a C-terminal product of the endolysin. In these cases, the heteromeric endolysins are composed typically by one subunit of the full-length polypeptide, and three copies of the smaller polypeptide. Based on a handful of examples of endolysins with diverse domain architectures that carried putative ITSS, and which are produced by phages that infect clinically or industrially relevant bacteria, we have demonstrated that two different polypeptides are indeed produced from a single gene. These results suggest that this mechanism may be more frequent than anticipated. For one of the studied endolysins, we have also shown that the association of the two polypeptides, with one as a multimer, is necessary for full enzymatic activity. The biochemical analysis also showed that this heteromultimeric endolysin should be composed by one subunit of the full-length polypeptide and between four to six of the smaller polypeptides, indicating a structure never described before.
Descrição
Tese de mestrado, Biologia Molecular e Genética, Universidade de Lisboa, Faculdade de Ciências, 2021
Palavras-chave
Bacteriófagos Endolisinas Heteromérica Local interno de iniciação da tradução Enzimas líticas Teses de mestrado - 2021