Identification of heat-stable A-factor from Myxococcus xanthus.
AUTOR(ES)
Kuspa, A
RESUMO
The asg mutants of Myxococcus xanthus fail to produce a set of related substances called A-factor. A-factor is released into the medium and is required early in fruiting body development. Lacking A-factor, the asg mutants are defective in aggregation, sporulation, and expression of most genes whose products appear later than 1 h after development is induced by starvation. Previous work has shown that these defects are reversed when A-factor, released by developing wild-type cells, is added to asg mutant cells. Part of the material in conditioned medium with A-factor activity is heat stable and dialyzable. This low-molecular-weight A-factor consists of a mixture of amino acids and peptides. Fifteen single amino acids have A-factor activity, and 11 of these are found in conditioned medium. Mixtures of amino acids have a total activity approximately equal to the sum of the activities of their constituents. Conditioned medium also contains peptides with A-factor activity. Pure peptides have A-factor activity, and their specific activities are equal to or less than the sum of the activities of their constituent amino acids. There is no evidence for a specialized A-factor peptide in conditioned medium, one with a specific activity greater than the sum of its constituent amino acids. About half of the heat-stable A-factor activity in conditioned medium can be accounted for by free amino acids, and the remaining half can be accounted for by peptides. It is argued that heat-stable A-factor induces A-dependent gene expression not by the nutritional action of amino acids but through a chemosensory circuit.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=206001Documentos Relacionados
- The guanosine nucleotide (p)ppGpp initiates development and A-factor production in Myxococcus xanthus
- Enteroaggregative Escherichia coli heat-stable enterotoxin 1 represents another subfamily of E. coli heat-stable toxin.
- Chorismate Mutase from Streptomyces aureofaciens: a Heat-Stable Enzyme
- Heat-stable enterotoxins from Escherichia coli P16.
- Characteristics of heat-stable extracellular hemolysin from Pseudomonas aeruginosa.