Detection and Expression of Biosynthetic Genes in Actinobacteria ...

BERVANAKIS, G.Chapter 1: INTRODUCTIONA) Streptomyces griseusB)Step 1 Step 2 Step 3StreptomycinStreptomycinstreptoseFigure 10. A) Streptomycin (str) gene clusters of S. griseus N2-3-11 andS.glaucescens GLA.0. strB1 and strDELM represent biosynthetic genes; strA and strKrepresent resistance genes; strR and strS represent regulatory genes (adapted fromDistler et al., 1992). B) Streptomycin biosynthetic pathway in Streptomyces griseus.The genes involved in streptomycin biosynthesis are labelled as strD (dTDP-glucosesynthase); strE (dTDP-glucose-4,6-dehydratase); strM (dTDP-4-keto-6-deoxyglucose3,5-epimerase); strL (dTDP-dihydrostreptose synthase) (adapted from Johnson & Liu,1999).1.3.2.1 Aminoglycoside Deoxysugar Biosynthetic Genes inActinobacteriaIn actinobacteria the AG deoxysugar biosynthetic genes are found in a clusteredarrangement on chromosomal DNA (Figure 10A). The order of genes arefunctionally mixed, meaning that they are not arranged in pathway-specific operons(Distler et al., 1992). Genes coding for dTDP-glucose synthase (strD) and dTDP-Dglucose4,6 dehydratase (strE) are commonly found in AG deoxysugar antibiotics_____________________________________________________________________20