Is probably a dihydrostreptosyl glycosyltransferase, involved in the first glycosylation step condensing streptidine-6-phosphate and dihydrostreptose. dTDP-L-dihydrostreptose + streptidine 6-phosphate = dTDP + H(+) + O-(1->4)-alpha-L-dihydrostreptosyl-streptidine 6-phosphate Antibiotic biosynthesis; streptomycin biosynthesis.