Rat brain glutamic acid decarboxylase sequence deduced from a cloned cDNA

Area of Science:

• Neuroscience
• Molecular Biology
• Enzymology

Background:

• Glutamic acid decarboxylase (GAD) is a key enzyme in GABA synthesis in the brain.
• Understanding GAD's structure is crucial for studying neurotransmission and neurological disorders.
• Previous research focused on enzyme function, with limited information on its complete molecular structure.

Purpose of the Study:

• To determine the complete nucleotide sequence of the rat brain GAD mRNA.
• To analyze the predicted amino acid sequence of the rat GAD protein.
• To compare the rat GAD sequence with homologous sequences from other species.

Main Methods:

• Isolation of a rat brain cDNA expression library.
• Screening the library using an antibody specific to GAD.
• Nucleotide sequencing of the isolated cDNA clone.
• In vitro protein synthesis in Escherichia coli to confirm functionality.

Main Results:

• A cDNA clone encoding rat brain GAD was successfully isolated.
• The cDNA insert directs the synthesis of an active GAD protein in E. coli.
• The complete coding region of the rat GAD mRNA was sequenced.
• The predicted protein is 593 amino acids long.
• The N-terminal 557 amino acids show 95% identity to the cat GAD sequence.
• The C-terminal region (residues 557-593) of the rat GAD protein is unique and matches previously published partial rat peptide sequences.

Conclusions:

• The complete nucleotide sequence of rat brain GAD mRNA provides a valuable resource for molecular and neurobiological studies.
• The high sequence identity in the N-terminal region suggests conserved functional domains.
• The divergent C-terminal sequence indicates potential species-specific regulatory or functional differences in GAD.