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The nucleotide sequence of the Mr = 28,500 flagellin gene of Caulobacter crescentus
Abstract:
The DNA sequences which encode the Mr = 28,500 flagellin polypeptide of Caulobacter crescentus CB15 have been determined. The size of the protein, deduced from its DNA sequence (276 amino acids), is in agreement with its apparent molecular weight as measured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The distribution of arginine residues within the protein sequence encoded by the gene correlates with their relative location as predicted by peptide alignment analysis (Gill, P.R., and Agabian, N. (1982) J. Bacteriol. 150, 925-933). DNA sequences 5' and 3' to the coding sequence were also determined. In the 5' region, DNA sequences homologous to consensus sequences associated with RNA polymerase recognition and transcription initiation sites in Escherichia coli (Pribnow box) are found. These are centered around 60, 90, and 120 base pairs upstream from the ATG codon at the beginning of the structural gene. Sequences 3' to the coding region were identified which might signal transcription termination. A typical E. coli 16 S ribosomal binding site (Shine-Dalgarno sequence) is located just 5' to the coding sequence, and for most of the amino acids there is a strong codon usage preference. Although this protein is exported from the cell (Gill, P.R., and Agabian, N. (1982) J. Bacteriol. 150, 925-933), the encoded NH2-terminal amino acid sequence is not different from the mature product.
Insights
The DNA sequence for Caulobacter crescentus flagellin was determined, revealing its structure and regulatory elements. This analysis identified promoter and ribosomal binding sites crucial for gene expression.
Area of Science:
- Molecular Biology
- Bacteriology
- Genetics
Background:
- Flagellin is a major structural protein of bacterial flagella, essential for motility.
- Understanding flagellin gene regulation provides insights into bacterial development and adaptation.
Purpose of the Study:
- To determine the DNA sequence encoding the flagellin polypeptide of Caulobacter crescentus CB15.
- To identify regulatory sequences involved in flagellin gene expression and protein export.
Main Methods:
- DNA sequencing of the flagellin gene and flanking regions.
- Analysis of protein sequence deduced from DNA, comparing it with experimental data.
- Bioinformatic analysis to identify promoter, ribosomal binding, and termination signals.
Main Results:
- The complete DNA sequence of the Caulobacter crescentus flagellin gene (276 amino acids) was determined.
- Analysis revealed sequences homologous to E. coli promoter (Pribnow box) and ribosomal binding (Shine-Dalgarno) sites.
- Arginine residue distribution and codon usage preference were consistent with known protein characteristics and efficient translation.
Conclusions:
- The determined DNA sequence accurately predicts the flagellin protein's size and features.
- Identified upstream sequences suggest transcriptional regulation similar to E. coli.
- The flagellin is exported without N-terminal cleavage, indicating a unique secretion mechanism.