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Transmembrane Domain Oligomerization Propensity determined by ToxR Assay
Published on: May 26, 2011
Viable transmembrane region mutants of bacteriophage M13 coat protein prepared by site-directed mutagenesis
Abstract:
Bacteriophage M13 coat protein - a 50-residue protein located at the E. coli host membrane during phage reproduction - is subjected to cytoplasmic, membrane-bound, and DNA-interactive environments during the phage life cycle. In research to examine the specific features of primary/secondary structure in the effective transmembrane (TM) region of the protein (residues 21-39: YIGYAWAMVVVIVGATIGI) which modulate its capacity to respond conformationally to the progressive influences of these varying environments, we have prepared over two dozen viable mutant phages with alterations in their coat protein TM regions. Mutants were obtained through use of site-directed mutagenesis techniques in combination with three "randomized" oligonucleotides which spanned the TM region. No subcloning was required. Among mutations observed were those in which each of the four TM Val residues was changed to Ala, and several with increased Ser or Thr content, including one double Ser mutant (G23S-A25S). Polar substitutions arising at Gly23 and Tyr24-including G23D, Y24H, Y24D and Y24N-suggested that this local segment resides external to the host membrane. Milligram quantities of mutant coat proteins are obtained by growing M13 mutant phages in liter preparations, with isotopic (e.g., 13C) labelling at desired sites, for subsequent characterization and conformational analysis in membrane-mimetic media.
Insights
Researchers studied Bacteriophage M13 coat protein
Area of Science:
- Molecular Biology
- Structural Biology
- Biophysics
Background:
- The Bacteriophage M13 coat protein is crucial for phage reproduction within E. coli.
- This protein navigates diverse cellular environments: cytoplasmic, membrane-bound, and DNA-interactive.
Purpose of the Study:
- To investigate how the primary and secondary structure of the M13 coat protein's transmembrane (TM) region (residues 21-39) influences its conformational adaptability.
- To understand the TM region's response to varying host membrane environments.
Main Methods:
- Generated over two dozen mutant M13 phages using site-directed mutagenesis and randomized oligonucleotides targeting the TM region.
- Analyzed mutations including Val to Ala substitutions and increased Ser/Thr content (e.g., G23S-A25S).
- Investigated polar substitutions at Gly23 and Tyr24 (G23D, Y24H, Y24D, Y24N).
Main Results:
- Mutant phages with altered TM regions were successfully created without subcloning.
- Specific mutations, like polar substitutions at Gly23 and Tyr24, provided insights into the protein's location relative to the host membrane.
- Milligram quantities of mutant coat proteins, including isotopically labeled variants, were produced for further analysis.
Conclusions:
- The study successfully generated and characterized M13 coat protein mutants to probe TM region structure-function relationships.
- Findings suggest that certain residues in the TM region are exposed externally, influencing conformational changes.
- The methodology allows for detailed conformational analysis of mutant proteins in membrane-mimetic environments.
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