RESUMEN
Defensins are a large family of host defense peptides expressed in leukocytes and epithelia. Using P1 and BAC clones, we have determined the organization of the human alpha-defensin genes and the beta-defensin gene HDEFB1 on chromosome 8p23. From the telomere, the order of the genes (with encoded peptides in parentheses) is HDEFA5 (HD-5), HDEFA1/1A (HNP-1/3), HDEFA4 (HNP-4), HDEFA6 (HD-6), and HDEFB1 (HBD-1). These genes span a region of approximately 450kb. Genes encoding intestinal Paneth cell defensins (HDEFA5 and HDEFA6) flank the myeloid defensin gene cluster (HDEFA1, HDEFA1A, HDEFA4). Based on our previous studies, the remaining known defensin gene, HDEFB2 (HBD-2), is about 400kb centromeric to HDEFB1. This map supports the hypothesis, originally proposed because of sequence similarities, that myeloid alpha-defensin genes evolved by reduplication and divergence from Paneth cell defensin genes, and identifies regions and clones, which should be useful in the search for new defensin genes.
Asunto(s)
Cromosomas Humanos Par 8 , Mapeo Contig , Proteínas/genética , alfa-Defensinas , beta-Defensinas , Secuencia de Bases , Cartilla de ADN , Defensinas , Evolución Molecular , Humanos , Reacción en Cadena de la PolimerasaRESUMEN
Epithelial beta-defensins are broad-spectrum cationic antimicrobial peptides that also act as chemokines for adaptive immune cells. In the human genome, all known defensin genes cluster to a <1 Mb region of chromosome 8p22-p23. To identify new defensin genes, the DNA sequence from a contig of large-insert genomic clones from the region containing human beta-defensin-2 (HBD-2) was analyzed for the presence of defensin genes. This sequence survey identified a novel beta-defensin, termed HBD-3. The HBD-3 gene contains two exons, is located 13 kb upstream from the HBD-2 gene, and it is transcribed in the same direction. A partial HBD-3 cDNA clone was amplified from cDNA derived from IL-1beta induced fetal lung tissue. The cDNA sequence encodes for a 67 amino acid peptide that is approximately 43% identical to HBD-2 and shares the beta-defensin six cysteine motif. By PCR analysis of two commercial cDNA panels, HBD-3 expression was detected in adult heart, skeletal muscle, placenta and in fetal thymus. From RT-PCR experiments, HBD-3 expression was observed in skin, esophagus, gingival keratinocytes, placenta and trachea. Furthermore, in fetal lung explants and gingival keratinocytes, HBD-3 mRNA expression was induced by IL-1beta. Additional sequence analysis identified the HE2 (human epididymis secretory protein) gene 17 kb upstream from the HBD-3 gene. One splice variant of this gene (HE2beta1) encodes a beta-defensin consensus cysteine motif, suggesting it represents a defensin gene product. HE2beta1 mRNA expression was detected in gingival keratinocytes and bronchial epithelia using RT-PCR analysis. The discovery of these novel beta-defensin genes may allow further understanding of the role of defensins in host immunity at mucosal surfaces.
Asunto(s)
Proteínas Portadoras , Genómica , Proteínas Recombinantes , beta-Defensinas/genética , Adulto , Secuencia de Aminoácidos , Antígenos de Superficie/genética , Secuencia de Bases , Mapeo Contig , ADN/química , ADN/genética , Exones , Femenino , Feto/metabolismo , Expresión Génica , Regulación del Desarrollo de la Expresión Génica , Genes/genética , Biblioteca Genómica , Glicopéptidos/genética , Glicoproteínas , Humanos , Intrones , Masculino , Datos de Secuencia Molecular , ARN Mensajero/genética , ARN Mensajero/metabolismo , Alineación de Secuencia , Análisis de Secuencia de ADN , Homología de Secuencia de Aminoácido , Distribución Tisular , Proteínas de Transporte VesicularRESUMEN
Defensins are a family of microbicidal peptides abundant in the granules of mammalian neutrophils, in rabbit alveolar macrophages, and in human and murine intestinal Paneth cells. We cloned and sequenced the genes of three neutrophil-specific defensins. Human HNP-1 and HNP-3 are nearly identical and rabbit NP-3a is closely related. The four known neutrophil-specific defensin genes are strikingly similar in the structure and organization of their three exons and two introns, but the three defensin genes expressed in macrophages (MCP-1 and -2) or Paneth cells (HD-5) are organized differently: HD-5 had only two exons, and MCP-1 and -2 have a comparatively short first intron. The diverse genomic organization of defensin genes may contribute to their cell-specific expression.
Asunto(s)
Proteínas Sanguíneas/genética , Neutrófilos/fisiología , alfa-Defensinas , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Clonación Molecular , Defensinas , Escherichia coli/genética , Fibroblastos/fisiología , Biblioteca Genómica , Humanos , Pulmón/fisiología , Macrófagos Alveolares/fisiología , Masculino , Ratones , Datos de Secuencia Molecular , Regiones Promotoras Genéticas , Conejos , Homología de Secuencia de Ácido Nucleico , Espermatozoides/fisiologíaRESUMEN
We overexpressed the CheY protein by fusing the cheY gene to the tryptophan promoter from Serratia marcescens. Expression of the trp promoter-cheY fusion and subsequent purification of the protein resulted in the isolation of up to 20 mg of homogeneously pure CheY protein from 100 mg of the cytoplasmic supernatant fraction. Purification of the CheY protein was accomplished by exploiting the affinity of CheY protein to cibacron blue dye and molecular sieve chromatography. Preliminary biochemical characterization of the pure CheY protein revealed specific interactions with S-adenosylmethionine and cibacron blue dye. Additional kinetic analysis showed that CheY protein inhibits EcoRI methyltransferase. The amino acid composition of the CheY protein predicted by the DNA sequence of the cheY gene and the amino acid analysis of the CheY protein were in agreement, confirming the authenticity of the purified CheY protein.