A heterodimer of EsxA and EsxB is involved in sporulation and is secreted by a type VII secretion system in Streptomyces coelicolor.
An esx locus, related to the multiple esx loci of Mycobacterium tuberculosis, is conserved in all sequenced Streptomyces genomes, where it is associated with the developmental regulatory gene bldB. Here we demonstrate that the esxBA operon, comprising part of the locus, has a novel morphogenetic function in the model species Streptomyces coelicolor. This operon encodes two proteins belonging to the WXG-100 superfamily that can form a heterodimer and are secreted in the absence of signal sequences. A mutation in esxBA results in a delay in sporulation, with eventual development of aerial hyphae with chains of abnormally sized spore compartments possessing irregular DNA contents. During early sporulation, expression of the operon is elevated in a bldB mutant. Other genes in the locus, notably SCO5734 and SCO5721, encode components of a type VII secretion system. Disruption of either of these genes prevents secretion of EsxAB but has no effect on sporulation. To explain the morphogenetic function of EsxAB, we propose that the heterodimer sequesters a regulator of expression of genes involved in nucleoid organization during sporulation.
Institute of Life Science, School of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, UK.
Sandra
S
Akpe San Roman
Institute of Life Science, School of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, UK.
Paul D
PD
Facey
Institute of Life Science, School of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, UK.
Lorena
L
Fernandez-Martinez
Department of Biomedical Research, Center of Pharmaceutical Chemistry, Atabey, Playa, PO Box 6990, Havana, Cuba.
Caridad
C
Rodriguez
Department of Biomedical Research, Center of Pharmaceutical Chemistry, Atabey, Playa, PO Box 6990, Havana, Cuba.
Carlos
C
Vallin
Institute of Life Science, School of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, UK.
Ricardo
R
Del Sol
Institute of Life Science, School of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, UK.
Paul
P
Dyson
D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D019281:Dimerization; D009154:Mutation; D009876:Operon; D048372:Streptomyces coelicolor / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
D001426:Bacterial Proteins