Transcriptional activation of the fatty acid biosynthetic genes in Streptomyces coelicolor

COMBA S., D'ANGELO, M., ARABOLAZA, A. GRAMAJO. H

Huerta Grande-Cordoba

Congreso; XLIV Reunión Anual de la Sociedad Argentina de Bioquímica y Biología Molecular (SAIB; 2008

Sociedad Argentina de Bioquímica y Biología Molecular

Fatty acid biosynthesis is not only an essential process for most living cells, but it is also energetically expensive. Thus organisms have developed homeostatic mechanisms that maintain the concentration of lipids at particular levels. In Streptomyces coelicolor the essential FAS genes are clustered at a single location within its genome (fab operon). Bioinformatics analysis of the fab genes locus revealed the presence of a highly conserved open reading frame located upstream of fabD, named fasA, which has homology with transcriptional regulators. To investigate the functional role of FasA in the transcriptional regulation of the fab operon, we initially constructed a fasA disruption mutant (AM6). This strain showed an evident reduction in vegetative growth rate and a delay in the onset of sporulation. AM6 also presented diminished FAS activity, distorted composition of total fatty acids and reduced triacylgliceride content compared to the wild type strain. Further the analysis of a transcriptional fusion to fabD showed an 8-fold reduction in its expression in AM6 cells. To confirm that this effect was exclusively related to the absence of FasA, we complemented the AM6 mutant. In this genetic background the fabD transcription, as well as the growth rate, was restored to the wild type levels. All these results suggest that FasA is involved in transcriptional activation of fab operon.