A chaperone in the HSP70 family controls production of extracellular fibrils in Myxococcus xanthus.
Three independent Tn5-lac insertions in the S1 locus of Myxococcus xanthus inactivate the sglK gene, which is nonessential for growth but required for social motility and multicellular development. The sequence of sglK reveals that it encodes a homologue of the chaperone HSP70 (DnaK). The sglK gene is cotranscribed with the upstream grpS gene, which encodes a GrpE homologue. Unlike sglK, grpS is not required for social motility or development. Wild-type M. xanthus is encased in extracellular polysaccharide filaments associated with the multimeric fibrillin protein. Mutations in sglK inhibit cell cohesion, the binding of Congo red, and the synthesis or secretion of fibrillin, indicating that sglK mutants do not make fibrils. The fibR gene, located immediately upstream of the grpS-sglK operon, encodes a product which is predicted to have a sequence similar to those of the repressors of alginate biosynthesis in Pseudomonas aeruginosa and Pseudomonas putida. Inactivation of fibR leads to the overproduction of fibrillin, suggesting that M. xanthus fibril production and Pseudomonas alginate production are regulated in analogous ways. M. xanthus and Pseudomonas exopolysaccharides may play similar roles in a mechanism of social motility conserved in these gram-negative bacteria.
Department of Microbiology, Molecular Biology and Biochemistry, University of Idaho, Moscow, Idaho 83844-3052, USA.
R M
RM
Weimer
C x
Cx
Creighton
A
A
Stassinopoulos
P
P
Youderian
P L
PL
Hartzell
D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D002454:Cell Differentiation / Q000235:genetics; D002465:Cell Movement / Q000235:genetics; D000071837:Fibrillins; D005786:Gene Expression Regulation; D005798:Genes, Bacterial; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D008840:Microfilament Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D016941:Myxococcus xanthus / Q000235:genetics* / Q000648:ultrastructure*; D009876:Operon; D020161:Physical Chromosome Mapping; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis; D012097:Repressor Proteins; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
D001426:Bacterial Proteins; C115002:FibR protein, Myxococcus xanthus; D000071837:Fibrillins; C115003:GrpS protein, Myxococcus xanthus; D018840:HSP70 Heat-Shock Proteins; D008840:Microfilament Proteins; D011135:Polysaccharides, Bacterial; D012097:Repressor Proteins; C115004:SglK protein, Myxococcus xanthus