Structure of angiogenin dimer bound to double-stranded RNA

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Biology

Background:

• Angiogenin, an RNase A family member, has roles in various pathologies.
• Its RNA endonuclease activity is crucial but inefficient, potentially due to a C-terminal helix blocking the active site.
• The interaction mechanism between angiogenin and RNA remains poorly understood, with no prior structural data.

Purpose of the Study:

• To elucidate the structural basis of angiogenin-RNA interactions.
• To investigate the role of the C-terminal helix in angiogenin-RNA binding.
• To provide the first structural data on angiogenin bound to an RNA duplex.

Main Methods:

• X-ray crystallography was employed to determine the structure of angiogenin complexed with a double-stranded RNA duplex.
• Analysis of the crystal structure focused on the positioning of angiogenin relative to the RNA and conformational changes.

Main Results:

• The structure shows angiogenin bound to double-stranded RNA, but the RNA does not access the active site.
• No conformational rearrangement of angiogenin's C-terminal domain was observed upon RNA binding.
• A novel crystallographic dimer of angiogenin was identified, mediating interactions with the major and minor grooves of the RNA.

Conclusions:

• Angiogenin-RNA interaction does not involve direct active site engagement in this complex.
• The observed dimer formation is a key feature of angiogenin binding to double-stranded RNA.
• These findings reveal a new mode of RNA interaction for angiogenin, distinct from its catalytic function.