Assuntos
Bioquímica/métodos , Proteínas HMGA/química , Proteínas HMGA/isolamento & purificação , Nucleossomos/química , Nucleossomos/metabolismo , Motivos de Aminoácidos , Sequência de Aminoácidos , Animais , Cromatina/química , DNA/química , Histonas/química , Humanos , Espectrometria de Massas , Modelos Moleculares , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , Mutação , Peptídeos/química , Fosforilação , Ligação Proteica , Estrutura Terciária de Proteína , Proteínas Recombinantes/química , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Fatores de TempoRESUMO
Plant high-mobility-group (HMG) chromosomal proteins are the most abundant and ubiquitous nonhistone proteins found in the nuclei of higher eukaryotes. There are only two families of HMG proteins, namely, HMGA and HMGB in plants. The cDNA encoding wheat HMGa protein was isolated and characterized. Wheat HMGA cDNA encodes a protein of 189 amino acid residues. At its N terminus, there is a histone H1-like structure, which is a common feature of plant HMGA proteins, followed by four AT-hook motifs. Polymerase chain reaction results show that the gene contains a single intron of 134 bp. All four AT-hook motifs are encoded by the second exon. Northern blot results show that the expression of HMGA gene is much higher in organs undergoing active cell proliferation. Gel retardation analysis show that wheat HMGa, b, c and histone H1 bind to four-way-junction DNA with high binding affinity, but affinity is dramatically reduced with increasing Mg(2+) and Na(+) ion concentration. Competition binding studies show that proteins share overlapping binding sites on four-way-junction DNA. HMGd does not bind to four-way-junction DNA.
