Streptomyces is an attractive host for heterologous protein secretion. To further optimize its expression capacity, better expression vectors will be helpful. Here, based on pSGL1, a high copy number plasmid present in Streptomyces globisporus C-1027, we constructed a series of novel E. coli-Streptomyces shuttle expression vectors pIMB2-4. These vectors, which are compatible with pIJ-derived vectors, contain the strong promoter ermE*p and signal sequence SP (MelC1) of the first ORF of melanin operon in S. antibiotics (pIMB2), SP (CagA) of C-1027 apoprotein in S. globisporus C-1027 (pIMB3 and pIMB4). Using these vectors, human interleukin-6 (IL-6) could successfully be expressed and secreted using S. lividans TK24 as host. Furthermore, replacement of a rare leucine codon TTA with CTG in SP (CagA) enhanced IL-6 production.