Beschreibung:
<jats:title>ABSTRACT</jats:title>
<jats:p>
<jats:italic>Streptomyces reticuli</jats:italic>
has an inducible ATP-dependent uptake system specific for cellobiose and cellotriose. By reversed genetics a gene cluster encoding components of a binding protein-dependent cellobiose and cellotriose ABC transporter was cloned and sequenced. The deduced gene products comprise a regulatory protein (CebR), a cellobiose binding lipoprotein (CebE), two integral membrane proteins (CebF and CebG), and the NH
<jats:sub>2</jats:sub>
-terminal part of an intracellular β-glucosidase (BglC). The gene for the ATP binding protein MsiK is not linked to the
<jats:italic>ceb</jats:italic>
operon. We have shown earlier that MsiK is part of two different ABC transport systems, one for maltose and one for cellobiose and cellotriose, in
<jats:italic>S. reticuli</jats:italic>
and
<jats:italic>Streptomyces lividans</jats:italic>
. Transcription of polycistronic
<jats:italic>cebEFG</jats:italic>
and
<jats:italic>bglC</jats:italic>
mRNAs is induced by cellobiose, whereas the
<jats:italic>cebR</jats:italic>
gene is transcribed independently. Immunological experiments showed that CebE is synthesized during growth with cellobiose and that MsiK is produced in the presence of several sugars at high or moderate levels. The described ABC transporter is the first one of its kind and is the only specific cellobiose/cellotriose uptake system of
<jats:italic>S. reticuli</jats:italic>
, since insertional inactivation of the
<jats:italic>cebE</jats:italic>
gene prevents high-affinity uptake of cellobiose.
</jats:p>