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The Streptomyces ATP-binding component MsiK assists in cellobiose and maltose transport
A Schlösser1, T Kampers, H Schrempf
1FB Biologie/Chemie, Universität Osnabrück, Germany.
Abstract:
Streptomyces reticuli harbors an msiK gene which encodes a protein with an amino acid identify of 90% to a corresponding protein previously identified in Streptomyces lividans. Immunological studies revealed that S. lividans and S. reticuli synthesize their highest levels of MsiK during growth with cellobiose, but not with glucose. Moreover, moderate amounts of MsiK are produced by both species in the course of growth with maltose, melibiose, and xylose and by S. lividans in the presence of xylobiose and raffinose. In contrast, a recently identified cellobiose-binding protein and its distantly related homolog were only found if S. reticuli or S. lividans, respectively, was cultivated with cellobiose. Uptake of cellobiose and maltose was tested and ascertained for S. reticuli and S. lividans, but not for an msiK S. lividans mutant. However, transformants of this mutant carrying the S. reticuli or S. lividans msiK gene on a multicopy plasmid had regained the ability to transport both sugars. The data show that MsiK assists two ABC transport systems.
Insights
Streptomyces MsiK protein aids in transporting cellobiose and maltose. This protein, encoded by the msiK gene, is crucial for sugar uptake in Streptomyces species, particularly when grown on specific sugars.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- The msiK gene in Streptomyces reticuli encodes a protein homologous to one in Streptomyces lividans.
- MsiK protein levels are influenced by the carbon source during bacterial growth.
Purpose of the Study:
- To investigate the role of the MsiK protein in Streptomyces species.
- To determine the function of MsiK in sugar transport.
Main Methods:
- Immunological studies to quantify MsiK protein levels.
- Sugar uptake assays in wild-type and mutant strains.
- Genetic complementation using multicopy plasmids.
Main Results:
- MsiK protein expression is highest with cellobiose and moderate with other sugars like maltose and xylose.
- A Streptomyces lividans msiK mutant showed impaired cellobiose and maltose uptake.
- Complementation of the mutant with the msiK gene restored sugar transport capabilities.
Conclusions:
- MsiK protein plays a significant role in the function of two ABC transporter systems.
- MsiK is essential for efficient uptake of cellobiose and maltose in Streptomyces.