Gusmão Karla A G, Dos Santos Daniel M, Santos Virgílio M, Cortés María Esperanza, Reis Pablo V M, Santos Vera L, Piló-Veloso Dorila, Verly Rodrigo M, de Lima Maria Elena, Resende Jarbas M
Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG Brazil.
Instituto de Engenharia, Ciência e Tecnologia, Universidade Federal dos Vales do Jequitinhonha e Mucuri (UFVJM), Janaúba, MG Brazil.
J Venom Anim Toxins Incl Trop Dis. 2017 Jan 19;23:4. doi: 10.1186/s40409-017-0094-y. eCollection 2017.
The availability of antimicrobial peptides from several different natural sources has opened an avenue for the discovery of new biologically active molecules. To the best of our knowledge, only two peptides isolated from the frog , namely pentadactylin and ocellatin-F1, have shown antimicrobial activities. Therefore, in order to explore the antimicrobial potential of this species, we have investigated the biological activities and membrane interactions of three peptides isolated from the anuran skin secretion.
Three peptide primary structures were determined by automated Edman degradation. These sequences were prepared by solid-phase synthesis and submitted to activity assays against gram-positive and gram-negative bacteria and against two fungal strains. The hemolytic properties of the peptides were also investigated in assays with rabbit blood erythrocytes. The conformational preferences of the peptides and their membrane interactions have been investigated by circular dichroism spectroscopy and liposome dye release assays.
The amino acid compositions of three ocellatins were determined and the sequences exhibit 100% homology for the first 22 residues (ocellatin-LB1 sequence). Ocellatin-LB2 carries an extra Asn residue and ocellatin-F1 extra Asn-Lys-Leu residues at C-terminus. Ocellatin-F1 presents a stronger antibiotic potential and a broader spectrum of activities compared to the other peptides. The membrane interactions and pore formation capacities of the peptides correlate directly with their antimicrobial activities, i.e., ocellatin-F1 > ocellatin-LB1 > ocellatin-LB2. All peptides acquire high helical contents in membrane environments. However, ocellatin-F1 shows in average stronger helical propensities.
The obtained results indicate that the three extra amino acid residues at the ocellatin-F1 C-terminus play an important role in promoting stronger peptide-membrane interactions and antimicrobial properties. The extra Asn-23 residue present in ocellatin-LB2 sequence seems to decrease its antimicrobial potential and the strength of the peptide-membrane interactions.
从几种不同天然来源获得抗菌肽为发现新的生物活性分子开辟了一条途径。据我们所知，仅从青蛙中分离出的两种肽，即五指菌素和眼斑蛙素 - F1，显示出抗菌活性。因此，为了探索该物种的抗菌潜力，我们研究了从无尾两栖类皮肤分泌物中分离出的三种肽的生物活性和膜相互作用。
通过自动埃德曼降解法测定了三种肽的一级结构。这些序列通过固相合成制备，并针对革兰氏阳性和革兰氏阴性细菌以及两种真菌菌株进行活性测定。还通过兔血红细胞试验研究了这些肽的溶血特性。通过圆二色光谱法和脂质体染料释放试验研究了肽的构象偏好及其膜相互作用。
确定了三种眼斑蛙素的氨基酸组成，并且这些序列在前22个残基（眼斑蛙素 - LB1序列）上具有100％的同源性。眼斑蛙素 - LB2在C末端带有一个额外的Asn残基，而眼斑蛙素 - F1在C末端带有额外的Asn - Lys - Leu残基。与其他肽相比，眼斑蛙素 - F1具有更强的抗生素潜力和更广泛的活性谱。肽的膜相互作用和孔形成能力与其抗菌活性直接相关，即眼斑蛙素 - F1＞眼斑蛙素 - LB1＞眼斑蛙素 - LB2。所有肽在膜环境中都具有高螺旋含量。然而，眼斑蛙素 - F1平均显示出更强的螺旋倾向。
所得结果表明，眼斑蛙素 - F1 C末端额外的三个氨基酸残基在促进更强的肽 - 膜相互作用和抗菌特性方面起重要作用。眼斑蛙素 - LB2序列中存在的额外Asn - 23残基似乎降低了其抗菌潜力以及肽 - 膜相互作用的强度。
