The RNA splicing and processing endonuclease from Nanoarchaeum equitans (NEQ) belongs to the recently identified (ab)2 family of splicing endonucleases that require two different subunits for splicing activity. N. Equitans splicing endonuclease consists of the catalytic subunit (NEQ205) and the structural subunit (NEQ261). Here we report the crystal structure of the functional NEQ enzyme at 2.1 Angstroms resolution containing both subunits, as well as that of the NEQ261 subunit alone at 2.2 Angstroms resolution. The functional enzyme resembles previously known a2 and a4 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 homo-dimerization 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. / A Dissertation Submitted to the Institute of Molecular Biophysics in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy. / Summer Semester, 2009. / June 26, 2009. / RNA Cleavage, tRNA Splicing Endonuclease, RNA Processing / Includes bibliographical references. / Hong Li, Professor Directing Dissertation; Penny J. Gilmer, Outside Committee Member; Brian Miller, Committee Member; W. Ross Ellington, Committee Member; Branko Stefanovic, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_180587 |
| Contributors | Mitchell, Michelle Hall (authoraut), Li, Hong (professor directing dissertation), Gilmer, Penny J. (outside committee member), Miller, Brian (committee member), Ellington, W. Ross (committee member), Stefanovic, Branko (committee member), Program in Molecular Biophysics (degree granting department), Florida State University (degree granting institution) |
| Publisher | Florida State University, Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text |
| Format | 1 online resource, computer, application/pdf |
| Rights | This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). The copyright in theses and dissertations completed at Florida State University is held by the students who author them. |
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