Nucleotide sequence of the ampicillin resistance gene of Escherichia coli plasmid pBR322

Area of Science:

• Molecular Biology
• Genetics
• Microbiology

Background:

• The pBR322 plasmid in Escherichia coli confers ampicillin resistance.
• Penicillin beta-lactamase is the enzyme responsible for this resistance.
• Understanding the genetic basis of antibiotic resistance is crucial.

Purpose of the Study:

• To determine the complete nucleotide sequence of the ampicillin resistance gene in pBR322.
• To identify the protein product encoded by this gene.
• To investigate potential signal sequences for protein secretion.

Main Methods:

• Nucleotide sequencing of the ampicillin resistance gene from pBR322.
• Bioinformatic analysis to predict the encoded protein sequence.
• Comparison with independently determined partial amino acid sequences of the mature enzyme.

Main Results:

• The complete nucleotide sequence of the ampicillin resistance gene was elucidated.
• The gene encodes a protein of 286 amino acid residues.
• A putative signal sequence of 23 amino acids was identified at the N-terminus, absent in the mature enzyme.

Conclusions:

• The nucleotide sequence provides a complete genetic blueprint for the ampicillin resistance protein.
• The identified signal sequence suggests a mechanism for the secretion of penicillin beta-lactamase.
• This detailed sequence information aids in understanding plasmid-mediated antibiotic resistance in bacteria.