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Nucleic Acids Res. 2009 Aug;37(14):4787-98. doi: 10.1093/nar/gkp506. Epub 2009 Jun 10.

Functional importance of crenarchaea-specific extra-loop revealed by an X-ray structure of a heterotetrameric crenarchaeal splicing endonuclease.

Author information

  • 1Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan. yoshinas@m.u-tokyo.ac.jp

Abstract

Archaeal splicing endonucleases (EndAs) are currently classified into three groups. Two groups require a single subunit protein to form a homodimer or homotetramer. The third group requires two nonidentical protein components for the activity. To elucidate the molecular architecture of the two-subunit EndA system, we studied a crenarchaeal splicing endonuclease from Pyrobaculum aerophilum. In the present study, we solved a crystal structure of the enzyme at 1.7-A resolution. The enzyme adopts a heterotetrameric form composed of two catalytic and two structural subunits. By connecting the structural and the catalytic subunits of the heterotetrameric EndA, we could convert the enzyme to a homodimer that maintains the broad substrate specificity that is one of the characteristics of heterotetrameric EndA. Meanwhile, a deletion of six amino acids in a Crenarchaea-specific loop abolished the endonuclease activity even on a substrate with canonical BHB motif. These results indicate that the subunit architecture is not a major factor responsible for the difference of substrate specificity between single- and two-subunit EndA systems. Rather, the structural basis for the broad substrate specificity is built into the crenarchaeal splicing endonuclease itself.

PMID:
19515941
[PubMed - indexed for MEDLINE]
PMCID:
PMC2724299
Free PMC Article

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