RESUMO
Expression in Escherichia coli of the Myxococcus xanthus gene celA, which encodes an extracellular endoglucanase, resulted in CelA being distributed between cytoplasm, periplasm and membrane. The presence of an adjacent open reading frame downstream from the full celA gene, or the absence of a putative lipoprotein signal sequence, confined CelA distribution to the periplasm and membrane, or to the cytoplasm and periplasm, respectively.
Assuntos
Celulase/genética , Escherichia coli/genética , Myxococcus xanthus/genética , Sequência de Aminoácidos , Celulase/metabolismo , Clonagem Molecular , Escherichia coli/metabolismo , Regulação Enzimológica da Expressão Gênica , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Dados de Sequência Molecular , Myxococcus xanthus/química , Myxococcus xanthus/enzimologia , Fases de Leitura Aberta , Plasmídeos , Sinais Direcionadores de ProteínasRESUMO
An endoglucanase, CelA, is secreted by Myxococcus xanthus only during exponential growth. The production of this enzyme is decreased by mutations in 5 different genes (Exc +/- phenotype), three of which correspond to asg genes which regulate the production of an early cell-to-cell signal in development. Transcription of celA is decreased in two of these Exc +/- mutants, whereas a post-transcriptional step is affected in two other Exc- mutants. Thus, asg genes, in addition to regulating the onset of development, also regulate a gene (celA) that is expressed during exponential growth and that is not involved in development.
Assuntos
Celulase/genética , Regulação Bacteriana da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento , Regulação Enzimológica da Expressão Gênica , Myxococcus xanthus/genética , Fosfotransferases , Sequência de Aminoácidos , Proteínas de Bactérias/genética , Sequência de Bases , Northern Blotting , Caseínas/química , Celulase/biossíntese , Eletroforese , Dados de Sequência Molecular , Myxococcus xanthus/crescimento & desenvolvimento , Sistema Fosfotransferase de Açúcar do Fosfoenolpiruvato/biossíntese , Sistema Fosfotransferase de Açúcar do Fosfoenolpiruvato/genética , RNA/química , RNA Mensageiro/biossíntese , Análise de Sequência de DNA , Transdução de Sinais , Transcrição Gênica/genéticaRESUMO
The sequence of a 1955-bp TaqI DNA fragment from Myxococcus xanthus was determined. This fragment contains two complete genes, designated prtA and prtB. The prtA and prtB ORFs extend over 828 and 798 bp, respectively. They are separated only by 3 nt and appear to be present in a polycistronic transcriptional unit. A typical lipoprotein signal sequence is present at the N terminus of the two deduced polypeptides. The aa sequence of PrtA shows a high degree of identity to the region adjacent to the Ser residue belonging to the catalytic triad of serine proteases from Staphylococcus aureus and Enterococcus faecalis. It also exhibits features characteristic of trypsin-like serine proteases in that it contains the same pattern of variable and conserved regions. The deduced aa sequence of PrtB reveals a signature zinc-binding consensus motif (HEXXHXXGXXH/Met-turn) characteristic of the class of metalloproteases called metzincins. Plasmids containing prtA, prtB, or both were constructed. Protease activity studies of Escherichia coli clones containing these plasmids showed that both genes are necessary for this activity, whatever their cis or trans position. As prtB produces a putative membrane-bound lipoprotein of 266 aa, the protease activation must occur at the membrane level.