Probing the Conformational States of Thimet Oligopeptidase in Solution

Thimet oligopeptidase (TOP) is a metallopeptidase involved in the metabolism of oligopeptides inside and outside cells of various tissues. It has been proposed that substrate or inhibitor binding in the TOP active site induces a large hinge‐bending movement leading to a closed structure, in which the bound ligand is enclosed. The main goal of the present work was to study this conformational change, and fluorescence techniques were used. Four active TOP mutants were created, each equipped with a single‐Trp residue (fluorescence donor) and a p‐nitro‐phenylalanine (pNF) residue as fluorescence acceptor at opposite sides of the active site. pNF was biosynthetically incorporated with high efficiency using the amber codon suppression technology. Inhibitor binding induced shorter Donor‐Acceptor (D‐A) distances in all mutants, supporting the view that a hinge-like movement is operative in TOP. The activity of TOP is known to be dependent on the ionic strength of the assay buffer and D‐A distances were measured at different ionic strengths. Interestingly, a correlation between the D‐A distance and the catalytic activity of TOP was observed: the highest activities corresponded to the shortest D‐A distances. In this study for the first time the hinge‐bending motion of a metallopeptidase in solution could be studied, yielding insight about the position of the equilibrium between the open and closed conformation. This information will contribute to a more detailed understanding of the mode of action of these enzymes, including therapeutic targets like neurolysin and angiotensin‐converting enzyme 2 (ACE2)

Biochemical and structural analysis of Dermicidin-1L and its splice variant in biomimetic system.

Dermicidina (DCD) é um gene mapeado no cromossomo 12, lócus 12q13.1, e codifica uma proteína de 110 aminoácidos, que sofre um processamento proteolítico, gerando peptídeos ativos. O peptídeo C-terminal (DCD-1L) de 48 aminoácidos tem uma carga -2, e exerce função antibacteriana e antifúngica, e o peptídeo C-terminal splice variante, denominado DCD-SV de 59 aminoácidos, tem carga neutra, e suas propriedades ainda não foram estabelecidas. Neste trabalho são apresentados os resultados da expressão, purificação e sequenciamento da DCD nativa produzida em E. coli BL21 transformada com o vetor pAE-DCD. Na segunda parte são descritas as análises físico-químicas e bioquímicas da interação dos peptídeos sintéticos DCD-1L e DCD-SV com vesículas lipídicas gigantes e vesículas unilamelar grandes sintetizadas com palmitoil-oleoil-fosfatidilcolina. As preferenciais estruturais dos peptídeos foram investigadas por espectroscopia de Dicroísmo Circular. Nossos resultados sugerem que a DCD-SV tem alta propensão para adotar uma estrutura helicoidal permitindo sua inserção e oligomerização em membranas biomiméticas, e possível formação de canais de condutância molecular.Dermicidin (DCD) is mapped a gene on chromosome 12, locus 12q1.13 whose 110 amino acids protein is proteolytically processed to N and C-terminal peptides. The 48-amino acid C-terminal peptide (DCD-1L) has -2 net charges and display antibacterial and antifungal properties and the 59-amino acid splice variant C-terminal peptide (DCD-SV) has neutral net charge; however, its structure and biological function are unknown. Here we show the results of expression, purification and amino acid sequencing of recombinant DCD protein produced in E.coli transformed with pAE-DCD vector. We also describe the results of physical-chemical and biochemical analyses showing the visible differences between the interactions of DCD-1LL and DCD-SV synthetic peptides with giant unilamellar vesicles and large unilamellar vesciles made of palmitoyl-oleoyl phosphatidylcholine, used as biomimetic membranes. The structural preferences of peptides were analyzed by circular dichroism spectroscopy. Our results suggest that DCD-SV peptide has higher propensity to adopt helicoidal structure enabling it to insert into mimetic membranes, undergo oligomerization and formation of conductance channel

On the efficient bio-incorporation of 5-hydroxy-tryptophan in recombinant proteins expressed in Escherichia coli with T7 RNA polymerase-based vectors

Biosynthetic incorporation of non-canonic amino acids is an attractive strategy to introduce new properties in recombinant proteins. Trp analogs can be incorporated in recombinant proteins replacing regular Trp during protein translation into a Trp-auxotrophic cell host. This straightforward method however, is limited to few analogs recognized and accepted by the cellular protein production machinery. 5-hydroxy-tryptophan (50H-Trp) can be bio-incorporated using E. coli as expression host however; we have experienced very low incorporation yields - amount of protein containing regular Trp/amount of protein containing the Trp analog during expressions of 50H-Trp labeled proteins. Furthermore, this low incorporation yield were verified especially when the widely-used vectors based on the 17 RNA polymerase were used. Testing different 50H-Trp incorporation protocols we verified that in these T7 based systems, the production of the T7 RNA polymerase is driven by the same elements lac promoter/IPTG as the target protein. Consequently, the bio-incorporation of the 50H-Trp residues also occurs in this crucial enzyme, but, the produced T7 RNA polymerase labeled with 50H-Trp is inactive or much less active. In the present work, we describe an efficient method to overcome this mentioned problem and bio-incorporate 50H-Trp in proteins expressed in E. coli., using vectors based on the 17 RNA polymerase-T7 promoter. The two-step induction protocol here described showed incorporation efficiencies of 50H-Trp higher than 90%. (C) 2017 Elsevier Inc. All rights reserved