Proteins that rescue A-signal-defective mutants of Myxococcus xanthus.
The asg mutants of Myxococcus xanthus are defective in the production of an extracellular substance, called A-factor, that is required for expression of a set of fruiting body-specific genes. A-factor is released by wild-type cells (asg+) after 1 to 2 h of development. When A-factor is added to asg mutant cells, it restores expression of their A-factor-dependent genes. Rescue of beta-galactosidase production in an asg mutant carrying the A-factor-dependent lacZ transcriptional fusion (omega 4521) was used to assay A-factor activity. According to this assay, two types of substances with A-factor activity are present in conditioned medium. One type is heat stable and of low molecular weight; the other is heat labile and of high molecular weight. An approximately 27-kDa protein with heat-labile A-factor activity was purified from conditioned medium. The purified protein has proteolytic activity as well as A-factor activity. The substrate specificity of the 27-kDa protease resembles that of trypsin. A smaller protein with both heat-labile A-factor activity and proteolytic activity was identified. Its substrate specificity differs from that of the 27-kDa protein. In addition, trypsin and other proteases were found to have heat-labile A-factor activity. Trypsin inhibitory protein from soybeans neutralizes the A-factor activity of trypsin in parallel with its neutralization of protease activity, showing that the proteolytic activity of trypsin is necessary for its A-factor activity. The 27-kDa protein rescues the aggregation and sporulation defects of an asgB mutant in submerged culture as well as its ability to express beta-galactosidase from an asg-dependent lac fusion.
Plamann
L
L
Department of Biochemistry, Stanford University, California 94305.
Kuspa
A
A
Kaiser
D
D
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000502:physiology*; D001426:Bacterial Proteins / Q000302:isolation & purification / Q000494:pharmacology; D001681:Biological Assay; D002449:Cell Aggregation / Q000502:physiology; D002450:Cell Communication / Q000502:physiology*; D010450:Endopeptidases / Q000302:isolation & purification / Q000494:pharmacology; D006133:Growth Substances / Q000502:physiology*; D008969:Molecular Sequence Data; D009024:Morphogenesis / Q000502:physiology*; D009154:Mutation / Q000502:physiology*; D016941:Myxococcus xanthus / Q000187:drug effects / Q000502:physiology*; D013171:Spores, Bacterial / Q000187:drug effects / Q000502:physiology; D013379:Substrate Specificity; D014361:Trypsin Inhibitors / Q000494:pharmacology
D000596:Amino Acids; D001426:Bacterial Proteins; D006133:Growth Substances; D014361:Trypsin Inhibitors; D010450:Endopeptidases