Genetic mapping, cloning and physiological aspects of the glucose kinase gene of Streptomyces coelicolor

Abstract

Glucose kinase in Streptomyces coelicolor has a molecular weight of about 110,000. In crude extracts, the enzyme exhibited apparent K_m values of 0.20 mM for ATP, 0.27 mM for glucose, and 2.2 mM for the glucose analogue 2-deoxyglucose. Mutations (glk) to 2-deoxyglucose-resistance, which greatly reduce glucose kinase activity and result in relief of glucose repression of utilisation of various carbon sources, were mapped between proA and hisA in the S. coelicolor linkage map. Glucose kinase activity, 2-deoxyglucose-sensitivity, glucose utilisation and glucose repression, were all restored to glk mutants by a 3.5 kb DNA fragment cloned from S. coelicolor into a phage vector (ϕC31 KC515), and by larger (10–30 kb) fragments cloned into a low copy number plasmid vector (pIJ916). The glk gene was further localised to a 2.9 kb BclI fragment of the cloned DNA by sub-cloning. Part or all of this fragment was present in each of five primary plasmid clones tested.