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Nucleotide sequence of the genes III, VI and I of bacteriophage M13
Abstract:
A DNA region of 2750 base pairs encompassing the genes III, VI and I of bacteriophage M13 has been sequenced by the Maxam-Gilbert procedure. By establishing the nucleotide changes introduced by several amber mutations, the coding region and the regulatory signals of each gene have been deduced. The genes appear to span 1275 base pairs (gene III; mol.wt. 44,748) 339 base pairs (gene VI; mol.wt. 12,264) and 1047 base pairs (gene I; mol.wt. 39,500). Their separating non-codogenic regions are extremely short, namely two and one base pair, respectively. The C-terminal end of gene I, however, intrudes 23 nucleotides into gene IV. From the nucleotide sequence it appears that the minor capsid protein of the phage, which is encoded by gene III, is synthesized in a precursor form containing 18 extra amino acids at its N-terminal end. Furthermore, in this capsid protein two clusters of a fourfold repeat of the sequence Glu-Gly-Gly-Gly-Ser are apparent. Gene VI appears to code for a small, extremely hydrophobic polypeptide. Its total hydrophobic amino acids content of 51% suggests that this protein can only function in the host cell membrane.
Insights
This study sequenced bacteriophage M13 genes III, VI, and I, revealing their coding regions and regulatory signals. Gene III encodes a minor capsid protein precursor, while gene VI codes for a hydrophobic membrane protein.
Area of Science:
- Molecular Biology
- Virology
- Genetics
Background:
- Bacteriophage M13 is a well-studied model organism for DNA replication and gene expression.
- Understanding the genetic organization of bacteriophages is crucial for viral research.
Purpose of the Study:
- To sequence and analyze the DNA region containing genes III, VI, and I of bacteriophage M13.
- To identify the coding regions, regulatory signals, and protein products of these genes.
Main Methods:
- DNA sequencing using the Maxam-Gilbert procedure.
- Analysis of nucleotide changes from amber mutations to deduce gene structures.
Main Results:
- Sequenced a 2750 base pair DNA region of bacteriophage M13.
- Determined the nucleotide sequences and sizes of genes III (1275 bp), VI (339 bp), and I (1047 bp).
- Identified short non-coding regions between genes and an overlap between gene I and gene IV.
Conclusions:
- Gene III encodes a minor capsid protein synthesized as a precursor with an N-terminal extension.
- Gene VI likely codes for a hydrophobic membrane protein, suggested by its amino acid composition.
- The deduced genetic organization provides insights into bacteriophage M13 gene expression and protein function.