RESUMO
A series of gramicidin S derivatives 4-15 are presented that have four ornithine residues as polar protonated side chains and two central hydrophobic amino acids with unaltered turn regions. These peptides were screened against human erthrocytes and our standard panel of Gram negative- and Gram positive bacteria, including four MRSA strains. Based on the antibacterial- and hemolytic data, peptides 13 and 14 have an improved biological profile compared to the clinically applied topical antibiotic gramicidin S.
Assuntos
Antibacterianos/química , Gramicidina/análogos & derivados , Gramicidina/química , Antibacterianos/síntese química , Antibacterianos/farmacologia , Eritrócitos/efeitos dos fármacos , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Positivas/efeitos dos fármacos , Gramicidina/síntese química , Gramicidina/farmacologia , Hemólise , Humanos , Testes de Sensibilidade Microbiana , Peptídeos/síntese química , Peptídeos/química , Peptídeos/farmacologiaRESUMO
Monobenzylated sugar amino acids (SAAs) that differ in ether ring size (containing an oxetane, furanoid, and pyranoid ring) were synthesized and incorporated in one of the ß-turn regions of the cyclo-decapeptide gramicidin S (GS). CD, NMR spectroscopy, modeling, and X-ray diffraction reveal that the ring size of the incorporated SAA moieties determines the spatial positioning of their cis-oriented carboxyl and aminomethyl substituents, thereby subtly influencing the amide linkages with the adjacent amino acids in the sequence. Unlike GS itself, the conformational behavior of the SAA-containing peptides is solvent dependent. The derivative containing the pyranoid SAA is slightly less hydrophobic and displays a diminished haemolytic activity, but has similar antimicrobial properties as GS.
Assuntos
Aminoácidos/química , Anti-Infecciosos/química , Anti-Infecciosos/síntese química , Gramicidina/química , Oligopeptídeos/química , Oligopeptídeos/síntese química , Sequência de Aminoácidos , Amino Açúcares , Dicroísmo Circular , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Conformação Molecular , Estrutura Molecular , Difração de Raios XRESUMO
In this paper, we describe the crystal structure of previously reported ring-extended gramicidin S (GS) derivative 2 (GS14K4), containing a d-amino acid residue in one of the ß-strand regions. This structure is in agreement with a previously reported modeling study of the same molecule. The polar side chain of the additional d-amino acid residue is positioned at the same face of the molecule as the hydrophobic side chains, and we believe that because of this compound 2 is considerably less hydrophobic than extended GS derivatives in which the strand regions are exclusively composed of l-amino acids. Using this backbone structure as our benchmark we prepared a small series of ring-extended GS analogues featuring sugar amino acid dipeptide isosteres of varied hydrophobicity at the turn region. We show that via this approach hydrophobicity of extended GS analogues can be tuned without affecting the secondary structure (as observed from NMR and CD spectra). Biological evaluation reveals that hydrophobicity correlates to cell toxicity, but still bacteriolysis is induced with GS analogues that are too hydrophilic to efficiently lyse human red blood cells.
Assuntos
Antibacterianos/síntese química , Gramicidina/análogos & derivados , Antibacterianos/química , Antibacterianos/farmacologia , Dicroísmo Circular , Cristalografia por Raios X , Eritrócitos/efeitos dos fármacos , Gramicidina/química , Gramicidina/farmacologia , Humanos , Interações Hidrofóbicas e Hidrofílicas , Testes de Sensibilidade Microbiana , Estrutura Secundária de Proteína , Estrutura Terciária de ProteínaRESUMO
The cyclic cationic antimicrobial peptide gramicidin S (GS) is an effective topical antibacterial agent that is toxic for human red blood cells (hemolysis). Herein, we present a series of amphiphilic derivatives of GS with either two or four positive charges and characteristics ranging between very polar and very hydrophobic. Screening of this series of peptide derivatives identified a compound that combines effective antibacterial activity with virtually no toxicity within the same concentration range. This peptide acts against both Gram-negative and Gram-positive bacteria, including several MRSA strains, and represents an interesting lead for the development of a broadly applicable antibiotic.
Assuntos
Adamantano/química , Adamantano/farmacologia , Antibacterianos/química , Antibacterianos/farmacologia , Eritrócitos/efeitos dos fármacos , Gramicidina/química , Gramicidina/farmacologia , Hemólise/efeitos dos fármacos , Peptídeos/química , Peptídeos/farmacologia , Sequência de Aminoácidos , Aminoácidos , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Positivas/efeitos dos fármacos , Humanos , Modelos Moleculares , Permeabilidade , Relação Estrutura-AtividadeRESUMO
Ring extended Gramicidin S analogues containing adamantane amino acids and six cationic residues were designed and evaluated. Systematic replacement of the hydrophobic residues with adamantane amino acids resulted in a small set of compounds with varying amphipathic character. It was found that the amphipathicity of these compounds is correlated to their biological activity. Several bacterial strains including MRSA strains were shown to be killed by the novel peptides. The most potent antibacterial peptides are tetradecameric GS analogues containing six positives charges and two adamantane moieties.
Assuntos
Adamantano/química , Aminoácidos/química , Anti-Infecciosos/química , Gramicidina/análogos & derivados , Sequência de Aminoácidos , Anti-Infecciosos/farmacologia , Cátions/química , Dicroísmo Circular , Gramicidina/farmacologia , Interações Hidrofóbicas e Hidrofílicas , Staphylococcus aureus Resistente à Meticilina/efeitos dos fármacosRESUMO
The fact that GPCRs might function in a dimeric fashion is currently well accepted. For GnRHR, a GPCR that regulates gonadotropin release, there is evidence that the receptor also functions as a dimer. We here describe the design and synthesis of a set of dimeric GnRHR antagonists in order to understand the interaction of dimeric ligands to the receptor and to address the question whether GnRHR dimerization is a prerequisite for signalling. Biological evaluation of the compounds shows no discrimination between monomeric and dimeric-ligands in respect to binding affinities, however, the dimeric ligands appear to have different functional properties.
Assuntos
Benzeno/síntese química , Benzeno/farmacologia , Pargilina/química , Receptores LHRH/antagonistas & inibidores , Receptores LHRH/metabolismo , Aminoácidos/química , Animais , Benzeno/química , Células CHO , Sobrevivência Celular/efeitos dos fármacos , Cricetinae , Cricetulus , Bases de Dados de Proteínas , Dimerização , Humanos , Iodetos/química , Ligantes , Estrutura Molecular , Relação Estrutura-AtividadeRESUMO
Two series of dimeric ligands for a G-protein-coupled receptor were prepared that differ by the interconnecting spacer system. Biological evaluation revealed that both dimeric series exhibit unique biological properties relative to their monomeric counterparts.The luteinizing hormone receptor (LHR), the follicle-stimulating hormone receptor (FSHR), and the thyroid-stimulating hormone receptor (TSHR) belong to the glycoprotein hormone receptor (GpHR) family. A prominent feature of all endogenous glycoprotein ligands is that they share an identical alpha subunit and acquire their selectivity from the unique beta subunit. Recent developments in pro-fertility research have led to the discovery of several low-molecular-weight agonists for the luteinizing hormone/choriogonadotropin receptor that bind to the transmembrane (TM) region of the LHR. Interestingly, some of these agonists are also able to activate the FSHR. Several research groups have shown that ligand dimerization presents a powerful tool to increase the subtype selectivity for structurally related G-protein-coupled receptors. In this work, we applied the dimerization strategy to GpHRs and explored the effect on receptors with closely related TM regions. Two series of dimeric ligands were prepared that differ in the interconnecting spacer system. Biological evaluation revealed that both series exhibit unique selectivity properties for the LHR, originating from either decreased potency or a decreased efficacy toward the FSHR.