ABSTRACT
Lincomycin A is a clinically important antimicrobial agent produced by
Streptomyces lincolnensis
. In this study, a new regulator designated LmbU (GenBank accession no. ABX00623.1) was identified and characterized to regulate lincomycin biosynthesis in
S. lincolnensis
wild-type strain NRRL 2936. Both inactivation and overexpression of
lmbU
resulted in significant influences on lincomycin production. Transcriptional analysis and
in vivo
neomycin resistance (Neo
r
) reporter assays demonstrated that LmbU activates expression of the
lmbA
,
lmbC
,
lmbJ
, and
lmbW
genes and represses expression of the
lmbK
and
lmbU
genes. Electrophoretic mobility shift assays (EMSAs) demonstrated that LmbU can bind to the regions upstream of the
lmbA
and
lmbW
genes through the consensus and palindromic sequence 5′-CGCCGGCG-3′. However, LmbU cannot bind to the regions upstream of the
lmbC
,
lmbJ
,
lmbK
, and
lmbU
genes as they lack this motif. These data indicate a complex transcriptional regulatory mechanism of LmbU. LmbU homologues are present in the biosynthetic gene clusters of secondary metabolites of many other actinomycetes. Furthermore, the LmbU homologue from
Saccharopolyspora erythraea
(GenBank accession no. WP_009944629.1) also binds to the regions upstream of
lmbA
and
lmbW
, which suggests widespread activity for this regulator. LmbU homologues have no significant structural similarities to other known cluster-situated regulators (CSRs), which indicates that they belong to a new family of regulatory proteins. In conclusion, the present report identifies LmbU as a novel transcriptional regulator and provides new insights into regulation of lincomycin biosynthesis in
S. lincolnensis
.
IMPORTANCE
Although lincomycin biosynthesis has been extensively studied, its regulatory mechanism remains elusive. Here, a novel regulator, LmbU, which regulates transcription of its target genes in the lincomycin biosynthetic gene cluster (
lmb
gene cluster) and therefore promotes lincomycin biosynthesis, was identified in
S. lincolnensis
strain NRRL 2936. Importantly, we show that this new regulatory element is relatively widespread across diverse actinomycetes species. In addition, our findings provide a new strategy for improvement of yield of lincomycin through manipulation of LmbU, and this approach could also be evaluated in other secondary metabolite gene clusters containing this regulatory protein.
AdpAlin, a Pleiotropic Transcriptional Regulator, Is Involved in the Cascade Regulation of Lincomycin Biosynthesis in Streptomyces lincolnensis