RESUMO
The prepeptide NukA of the lantibiotic nukacin ISK-1 consists of an N-terminal leader peptide followed by a propeptide moiety that undergoes post-translational modifications, that is, formation of unusual amino acids by NukM, cleavage of the leader peptide and transport by NukT to yield a mature peptide. To identify the region and conformation required for the maturation of prepeptide, we expressed a series of NukA mutants, mutants with the N-terminus-truncated leader peptide and site-directed mutants with conserved residues in the leader peptide of type A(II) lantibiotics, which were evaluated on the basis of the production of nukacin ISK-1. In addition, the secondary structure data of NukA mutants or fragments were obtained by circular dichroism spectra. The results indicated the importance of the alpha-helical leader peptide with hydrophobic and hydrophilic orientation consisting of the conserved residues in type A(II) lantibiotics. The expression data from various combinations of the chimeric prepeptides consisting of NukA and LctA (the prepeptide of lacticin 481, which shows high identity with NukA) further revealed that the amino acid difference at the C-terminus of the propeptide moiety between NukA and LctA, especially His at position 15 and Phe at position 19, was important for the maturation processes by the nukacin ISK-1 biosynthetic enzymes. Our findings suggest that the determinants in NukA were critically involved in the biosynthesis of nukacin ISK-1 and would thus be important for recognition by the nukacin ISK-1 biosynthetic enzymes.
Assuntos
Bacteriocinas/química , Bacteriocinas/metabolismo , Sequência de Aminoácidos , Bacteriocinas/genética , Cromatografia Líquida , Dicroísmo Circular , Eletroforese em Gel de Poliacrilamida , Espectrometria de Massas , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , Processamento de Proteína Pós-Traducional , Sinais Direcionadores de Proteínas/genética , Estrutura Secundária de Proteína , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Homologia de Sequência de AminoácidosRESUMO
AIMS: This study was performed to elucidate whether mitogen-activated protein kinases (MAPKs) are involved in the modulation of the proliferation and differentiation of skeletal muscle cells by fatty acids. MAIN METHODS: C2C12 myoblasts were cultured in differentiation medium containing 2% horse serum for 3 days, and treated with each fatty acid. Phosphorylation levels of MAPKs were examined by immunoblot analysis. KEY FINDINGS: The mono-unsaturated fatty acids (MUFAs), oleic acid (OA) and n-6 polyunsaturated fatty acids (n-6 PUFAs), linoleic acid (LA), gamma-linoleic acid (GLA), and arachidonic acid (AA) increased the proliferation of C2C12 cells. On the other hand, n-3 polyunsaturated fatty acids (n-3 PUFAs) and saturated fatty acids (SFs) did not affect the proliferation of C2C12 cells. In addition, the treatment of cis-9, trans-11 conjugated linoleic acid (c9,t11 CLA) showed an increased cell proliferation. However, trans-10, cis-12 conjugated linoleic acid (t10,c12 CLA) significantly inhibited cell proliferation. Treatment of C2C12 cells with LA, OA, and c9,t11 CLA increased phosphorylation levels of ERK1/2 and JNK during proliferation. During cell differentiation, OA, LA, and c9,t11 CLA stimulated differentiation of C2C12 cells, whereas t10,c12 CLA inhibited differentiation. We also found that OA, LA, and c9, t11 CLA increased phosphorylation level of ERK1/2, but not JNK during differentiation. SIGNIFICANCE: These results suggest that fatty acids are able to modulate the proliferation and differentiation of skeletal muscle and MAPKs may be involved in the modulation of the proliferation and differentiation of skeletal muscle cells by fatty acids.
