Structures of three human beta alcohol dehydrogenase variants. Correlations with their functional differences

Area of Science:

• Biochemistry
• Structural Biology
• Enzymology

Background:

• Human beta 1 alcohol dehydrogenase (ADH) is a crucial enzyme in alcohol metabolism.
• Genetic variations, particularly at position 47, influence ADH function and coenzyme binding.
• Understanding these structural differences is key to comprehending enzyme activity and substrate specificity.

Purpose of the Study:

• To determine the three-dimensional structures of three human beta ADH variants.
• To investigate the impact of amino acid substitutions at position 47 on enzyme structure and coenzyme interactions.
• To elucidate the molecular basis for altered coenzyme binding affinities in different ADH variants.

Main Methods:

• X-ray crystallography was employed to determine the structures of three human beta ADH variants to 2.5 A resolution.
• The variants studied included wild-type beta 1 ADH (Arg47), a naturally occurring variant (His47), and a site-directed mutant (Gly47).
• Structural comparisons focused on differences in amino acid residues at position 47 and their effects on protein-coenzyme binding.

Main Results:

• The His47 substitution resulted in a 100-fold decrease in coenzyme affinity with minimal structural changes.
• The Gly47 substitution led to structural alterations, including domain rotation and local side-chain movements, enhancing coenzyme binding.
• Position 47 significantly influences the strength of protein-coenzyme interactions, with distinct structural consequences for different substitutions.

Conclusions:

• Amino acid substitutions at position 47 profoundly impact human beta ADH structure and coenzyme binding affinity.
• The Gly47 variant's structural adaptations may compensate for reduced interactions, explaining its high coenzyme affinity.
• These findings provide insights into enzyme evolution, substrate specificity, and the development of enzyme inhibitors.