Mutational analysis of apolipoprotein B mRNA editing enzyme (APOBEC1). structure-function relationships of RNA...

Area of Science:

• Molecular Biology
• Enzymology
• RNA Editing

Background:

• APOBEC1 is the catalytic subunit of the enzyme complex responsible for apolipoprotein (apo) B mRNA editing.
• APOBEC1 requires dimerization and complementation factors for its in vitro editing activity.
• Understanding the structure-function relationship of APOBEC1 is key to elucidating its catalytic mechanism.

Purpose of the Study:

• To systematically analyze the structure-functional relationship of APOBEC1 through targeted mutagenesis.
• To identify critical sequence motifs and residues essential for apoB mRNA editing activity.
• To investigate the role of specific regions in APOBEC1 dimerization and enzyme catalysis.

Main Methods:

• Systematic targeted mutagenesis of APOBEC1 sequence motifs.
• In vitro RNA editing assays to assess enzyme activity.
• Deletion analysis and single amino acid substitutions to evaluate functional importance.
• Dimerization assays using amino and carboxy-terminal deletion mutants.

Main Results:

• Basic amino acid clusters (R15R17 and R33K34) in the amino-terminal region are essential for apoB mRNA editing.
• A carboxy-terminal region (residues 181-210), including a beta turn (P190A/P191A), is critical for editing function.
• Amino-terminal deletions up to A117 do not affect dimerization, while carboxy-terminal deletions diminish it.

Conclusions:

• Specific amino acid residues and motifs in both the amino and carboxy termini of APOBEC1 are crucial for its catalytic activity.
• The carboxy-terminal region, particularly a beta turn, plays a vital role in APOBEC1 function.
• APOBEC1 dimerization is influenced by its carboxy-terminal structure, impacting overall enzyme activity.