Crystal structure and assembly of the functional Nanoarchaeum equitans tRNA splicing endonuclease

Journal Article · Tue Oct 27 04:00:00 EDT 2009 · Nucleic Acids Res.

DOI:https://doi.org/10.1093/nar/gkp537· OSTI ID:1005945

Mitchell, Michelle; Xue, Song; Erdman, Rachel; Randau, Lennart; Söll, Dieter; Li, Hong

The RNA splicing and processing endonuclease from Nanoarchaeum equitans (NEQ) belongs to the recently identified ({alpha}{beta}){sub 2} family of splicing endonucleases that require two different subunits for splicing activity. N. equitans splicing endonuclease comprises the catalytic subunit (NEQ205) and the structural subunit (NEQ261). Here, we report the crystal structure of the functional NEQ enzyme at 2.1 {angstrom} containing both subunits, as well as that of the NEQ261 subunit alone at 2.2 {angstrom}. The functional enzyme resembles previously known {alpha}{sub 2} and {alpha}{sub 4} endonucleases but forms a heterotetramer: a dimer of two heterodimers of the catalytic subunit (NEQ205) and the structural subunit (NEQ261). Surprisingly, NEQ261 alone forms a homodimer, similar to the previously known homodimer of the catalytic subunit. The homodimers of isolated subunits are inhibitory to heterodimerization as illustrated by a covalently linked catalytic homodimer that had no RNA cleavage activity upon mixing with the structural subunit. Detailed structural comparison reveals a more favorable hetero- than homodimerization interface, thereby suggesting a possible regulation mechanism of enzyme assembly through available subunits. Finally, the uniquely flexible active site of the NEQ endonuclease provides a possible explanation for its broader substrate specificity.

• Research Organization: Argonne National Laboratory (ANL)
• Sponsoring Organization: USDOE
• OSTI ID: 1005945
• Journal Information: Nucleic Acids Res., Journal Name: Nucleic Acids Res. Journal Issue: (17) ; 2009 Vol. 37; ISSN 0305-1048; ISSN NARHAD
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

36 MATERIALS SCIENCE
CLEAVAGE
CRYSTAL STRUCTURE
DIMERS
ENDONUCLEASES
ENZYMES
FUNCTIONALS
PROCESSING
REGULATIONS
RNA
SPECIFICITY
SPLICING
SUBSTRATES