Structure and function of sawB, a gene involved in differentiation of Streptomyces ansochromogenes

A partial DNA library of Streptomyces ansochromogenes 7100 was constructed by using plasmid pIJ702 as vector and white mutant W19 as recipient. About 3 000 clones were obtained, two of which gave rise to the grey phenotype as wild type 7100. The plasmids were isolated from two transformants. The res ult indicated that the 5.2 kb and 5.8 kb DNA fragments were inserted into p IJ702. The resulting recombinant plasmids were designated as pNL-1 and pNL- 2 respectively. The 1.25 kb Pstl I-Apa I DNA fragment from pNL-1 was recogn ized as its complementarity to W19 strain. The nucleotide sequence of the 3 .0 kb Pst I DNA fragment including 1.25 kb was determined and analyzed. The result indicated that this DNA fragment contains one complete open reading frame (ORF1) which encodes a protein with 295 amino acid residues, and thi s gene was designated as sawB. The deduced protein has 81% amino acid ident ities in comparison with that encoded by whiH in Streptomyces coelicolor. T he function of sawB gene was studied by using strategy of gene disruption, and the resulting sawB mutant failed to form spores and produced loosely co iled aerial hyphal. The result showed that sawB is closely related to hypha l coiling and sporulation in S. ansochromogenes, and also indicated that th e sawB can complement whiH mutant (C119) to restore the grey phenotype of S treptomyces coelicolor J1501 (wild type).