SdeK, a Histidine Kinase Required for Myxococcus xanthus Development

Abstract

The sdeK gene is essential to the Myxococcus xanthus developmental process. We reported previously, based on sequence analysis (A. G. Garza, J. S. Pollack, B. Z. Harris, A. Lee, I. M. Keseler, E. F. Licking, and M. Singer, J. Bacteriol. 180:4628-4637, 1998), that SdeK appears to be a histidine kinase. In the present study, we have conducted both biochemical and genetic analyses to test the hypothesis that SdeK is a histidine kinase. An SdeK fusion protein containing an N-terminal polyhistidine tag (His-SdeK) displays the biochemical characteristics of a histidine kinase. Furthermore, histidine 286 of SdeK, the putative site of phosphorylation, is required for both in vitro and in vivo protein activity. The results of these assays have led us to conclude that SdeK is indeed a histidine kinase. The developmental phenotype of a ⌬sdeK1 strain could not be rescued by codevelopment with wild-type cells, indicating that the defect is not due to the mutant's inability to produce an extracellular signal. Furthermore, the ⌬sdeK1 mutant was found to produce both A-and C-signal, based on A-factor and codevelopment assays with a csgA mutant, respectively. The expression patterns of several Tn5lacZ transcriptional fusions were examined in the ⌬sdeK1-null background, and we found that all C-signaldependent fusions assayed also required SdeK for full expression. Our results indicate that SdeK is a histidine kinase that is part of a signal transduction pathway which, in concert with the C-signal transduction pathway, controls the activation of developmental-gene expression required to progress past the aggregation stage.

Mutations of the Act Promoter in Myxococcus xanthus

“…The very similar time course of the ⌬sdeK strain compared with DK10627, which has the wild-type allele of sdeK, indicates that act transcription does not depend on sdeK. The sdeK gene encodes a histidine protein kinase that has been shown to be essential for expression of many developmental genes (11,36,48). The substrate(s) for the putative sdeK kinase has not yet been identified, and the data in Fig.…”

DNA replication during sporulation in Myxococcus xanthus fruiting bodies

“…These observations might suggest that M. xanthus, like B. subtilis, has a regulatory circuit that prevents progression of development until DNA replication functions are fully completed. Of particular interest is that several developmental regulatory pathways are known to converge at the aggregation stage of development, including the C-signal (47) and SdeK (48) pathways and activation of the devTRS operon (49). The molecular mechanism of DNA replication coupling to development is undetermined, but it is possible that DNA replication is under the control of one or more of these regulatory pathways.…”

Mutations affecting predation ability of the soil bacterium Myxococcus xanthus

“…To test this hypothesis, we examined several known developmental mutants for their predation phenotypes. A mutant defective for SdeK, a histidine kinase required for integrating the cellular and population starvation responses (Pollack & Singer, 2001), was examined, as well as mutants in AsgA and CsgA, which are required for A-signal (Kuspa & Kaiser, 1989) and C-signal (Hagen & Shimkets, 1990) production, respectively; these data are presented in Fig. 1(a).…”

“…These three genes are known to regulate the major early regulatory circuits in M. xanthus development. In addition, we assayed mutants for two CsgA-and SdeK-dependent genes, devRS (Thöny-Meyer & Kaiser, 1993) and 4406 (Kroos et al, 1986;Pollack & Singer, 2001), which are activated at around 12 h after starvation initiation. Finally, we assayed mutants for a gene named phoP4 that is required for activating development-specific phosphatase activities 24 h into development (V. D. Pham and others, unpublished results).…”