THE SMALL PROTEIN SCO2038 CONTROLS TRYPTOPHAN BIOSYNTHESIS AND DIFFERENTIATION IN STREPTOMYCES COELICOLOR

The cellular regulatory factors comprise regulatory proteins, small RNA and small proteins. It is known that the product of small orfs (smorfs) can regulate the translation of downstream elements and also can encode functional peptides involved in the regulation of specific pathways (Ladoukakis E. et al.,2011). In particular, in the model streptomycete Sfreptomyces coelicolor, smorfs (about 100-300 nucleotides) were identified in some amino acid biosynthetic gene clusters such as in the tryptophan trpCXBA locus (Limauro D. et al., I 990; Hu DS. et al., 1999). In S. coelicolor the molecular mechanisms that regulate tryptophan (Trp) biosynthesis are poorly understood and, unlike the trp operon of Escherichia coli and Bacillus subtilis, the regulation of trp gene expression is not subjected to a feed-back control by the level of the end product. Thus, understanding the cellular lunction of the small orf sco2038 (trpX), could, shed light on molecular mechanisms that regulate the biosynthesis of tryptophan amino acid in S. coelicolor. To this purpose, phenotypic and molecular analyses were conducted on a S. coelicolor sco2038 mutant strain. In the light of proteomic and qRT-PCR results, this study indicates a new mechanism of tryptophan biosynthesis regulation suggesting that the small protein SC02038 could be the central modulator of tryptophan biosynthetic pathway.