The dasABC Gene Cluster, Adjacent to dasR , Encodes a Novel ABC Transporter for the Uptake of N , N ′-Diacetylchitobiose in Streptomyces coelicolor A3(2)

N ,N ′-Diacetylchitobiose [(GlcNAc)2 ] induces the transcription of chitinase (chi ) genes inStreptomyces coelicolor A3(2). Physiological studies showed that (GlcNAc)2 addition triggeredchi expression and increased the rate of (GlcNAc)2 concentration decline in culture supernatants of mycelia already cultivated with (GlcNAc)2 , suggesting that (GlcNAc)2 induced the synthesis of its own uptake system. Four open reading frames (SCO0531, SCO0914, SCO2946, and SCO5232) encoding putative sugar-binding proteins of ABC transporters were found in the genome by probing the 12-bp repeat sequence required for regulation ofchi transcription. SCO5232, nameddasA , showed transcriptional induction by (GlcNAc)2 andN ,N ′,N ‴-triacetylchitotriose [(GlcNAc)3 ]. Surface plasmon resonance analysis showed that recombinant DasA protein exhibited the highest affinity for (GlcNAc)2 (equilibrium dissociation constant [KD ] = 3.22 × 10−8 ). In thedasA -null mutant, the rate of decline of the (GlcNAc)2 concentration in the culture supernatant was about 25% of that in strain M145. The in vitro and in vivo data clearly demonstrated thatdasA is involved in (GlcNAc)2 uptake. Upstream and downstream ofdasA , the transcriptional regulator gene (dasR ) and two putative integral membrane protein genes (dasBC ) are located in the opposite and same orientations, respectively. The expression ofdasR anddasB , which seemed independent ofdasA transcription, was also induced by (GlcNAc)2 and (GlcNAc)3 .