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Structural aspects of aldehyde dehydrogenase that influence dimer-tetramer formation
Jose S Rodriguez-Zavala1, Henry Weiner
1Biochemistry Department, Purdue University, West Lafayette, Indiana 47907-1153, USA.
Biochemistry
|June 26, 2002
Summary
Aldehyde dehydrogenases (ALDHs) form dimers or tetramers. Hydrophobic interactions drive tetramer formation, with specific residues and C-terminal tails influencing ALDH stability and oligomerization.
Area of Science:
- Biochemistry
- Enzymology
- Protein Structure and Function
Background:
- Aldehyde dehydrogenases (ALDHs) exist as dimers or tetramers, with identical subunit structures.
- Tetrameric ALDHs (ALDH1, ALDH2) form a dimer of dimers (A-B + C-D), involving interactions like Ser500-Arg84.
- Dimeric ALDH3 lacks this interaction, potentially due to a C-terminal tail preventing tetramer formation.
Purpose of the Study:
- To investigate the forces maintaining ALDH tetramer formation.
- To understand the role of the C-terminal tail in ALDH3 oligomerization.
- To identify key residues involved in the dimer-dimer interface of tetrameric ALDHs.
Main Methods:
- Genetic manipulation: Deletion of C-terminal tail in ALDH3, addition of tails to ALDH1, and mutations at the dimer-dimer interface.
- Biophysical analysis: Gel filtration to assess oligomerization state, urea denaturation to evaluate protein stability.
- Enzyme kinetics: Determination of K(m) values for propionaldehyde and NAD+ for wild-type and mutant enzymes.
Main Results:
- Oligomerization state remained unchanged in most mutants and tail modifications.
- ALDH1 mutants showed reduced stability but altered NAD+ binding kinetics.
- A double mutant (D80G/S82A) exhibited concentration-dependent dimer-tetramer formation; the dimeric form was inactive, and the tetramer had 10% wild-type activity.
- Sequence alignment revealed increased hydrophobic surface area in tetrameric enzymes, suggesting hydrophobic interactions drive tetramer assembly.
- Residues 80 and 82 are critical for maintaining the tetramer post-assembly, while the C-terminal extension stabilizes the overall structure.
Conclusions:
- Hydrophobic interactions are the primary driving force for ALDH tetramer formation.
- Specific residues (e.g., D80, S82) and the C-terminal tail play crucial roles in ALDH oligomerization and stability.
- Understanding these structural determinants can inform the design of ALDH variants with altered oligomerization and activity.
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