Structure of puromycin-sensitive aminopeptidase and polyglutamine binding

Area of Science:

• Biochemistry
• Structural Biology
• Enzymology

Background:

• Puromycin-sensitive aminopeptidase (PSA) is a zinc metallopeptidase from the M1 family.
• PSA degrades bioactive peptides and proteasomal peptides, including polyglutamine.

Purpose of the Study:

• To determine the crystal structure of Puromycin-sensitive aminopeptidase (PSA).
• To elucidate the structural basis for PSA's substrate recognition and potential interactions.

Main Methods:

• X-ray crystallography was employed to determine the 3D structure of PSA at 2.3 Å resolution.
• Structural analysis focused on the enzyme's overall architecture, active site, and domain organization.
• Mutagenesis studies were performed to support structural findings regarding polyglutamine interaction.

Main Results:

• The crystal structure of PSA exhibits a V-shaped architecture with four M1 family domains, in a less compact conformation than other M1 aminopeptidases.
• A microtubule-binding sequence within the C-terminal HEAT repeat domain suggests potential tubulin interaction.
• The active site features an elongated groove with aromatic/hydrophobic residues and a large S1 subsite, indicating broad substrate recognition capabilities.
• Structural data, supported by mutation analysis, provides insight into polyglutamine binding.

Conclusions:

• The determined crystal structure of PSA offers a detailed view of its unique conformation and domain arrangement.
• The structural features suggest mechanisms for broad substrate specificity and potential interactions with cellular components like microtubules.
• This structural information is crucial for understanding PSA's biological roles and for potential therapeutic targeting.