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Sequence of gene malG in E. coli K12: homologies between integral membrane components from binding protein-dependent
Abstract:
The MalG protein is needed for the transport of maltose in Escherichia coli K12. We present the sequence of gene malG. The deduced amino acid sequence corresponds to a protein of 296 amino acid residues (mol. wt. = 32 188 daltons). This protein is largely hydrophobic (hydrophobic index = 0.83) and is thus presumably an integral inner membrane protein which could span the membrane through six hydrophobic segments. We provide direct evidence from fusion proteins for the translation frame and we also identified the in vitro made MalG protein. We have found a sequence which is highly conserved between MalG and MalF, the other integral inner membrane protein of the maltose transport system. This conserved sequence is also present in all known integral membrane proteins of binding protein-dependent transport systems, always at the same distance (approximately 90 residues) from their COOH terminus. We discuss briefly this finding.
Insights
The MalG protein, crucial for maltose transport in Escherichia coli K12, has been sequenced. Its hydrophobic nature suggests it
Area of Science:
- Molecular Biology
- Membrane Transport
- Bacterial Physiology
Background:
- Maltose transport in Escherichia coli K12 is essential for bacterial growth.
- The maltose transport system involves multiple proteins, including the integral inner membrane protein MalG.
- Understanding the structure and function of MalG is key to elucidating the maltose uptake mechanism.
Purpose of the Study:
- To present the nucleotide sequence of the Escherichia coli K12 malG gene.
- To characterize the deduced amino acid sequence and predict the secondary structure of the MalG protein.
- To investigate conserved regions within MalG and compare them to other integral membrane proteins involved in transport.
Main Methods:
- Gene sequencing of malG.
- Amino acid sequence analysis and prediction of hydrophobic segments.
- Construction and analysis of fusion proteins to confirm translation frame.
- Identification of the in vitro synthesized MalG protein.
- Sequence homology searches for conserved motifs.
Main Results:
- The malG gene encodes a protein of 296 amino acid residues with a molecular weight of 32,188 daltons.
- The MalG protein is highly hydrophobic, with a hydrophobic index of 0.83, suggesting it is an integral inner membrane protein with six transmembrane segments.
- Fusion protein analysis confirmed the translation frame, and the MalG protein was successfully identified in vitro.
- A highly conserved sequence was identified between MalG and MalF, another component of the maltose transporter.
- This conserved sequence is also found in homologous proteins of other binding protein-dependent transport systems.
Conclusions:
- The MalG protein is an integral inner membrane protein likely spanning the membrane multiple times.
- The identified conserved sequence in MalG and other transport proteins suggests a common structural or functional role in membrane translocation.
- Further investigation into this conserved region may provide insights into the general mechanism of binding protein-dependent transport systems.