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Exosite modules guide substrate recognition in the ZiPD/ElaC protein family
Oliver Schilling1, Bettina Späth, Brenda Kostelecky
1European Molecular Biology Laboratory Outstation Hamburg, Notkestrasse 85, 22603 Hamburg and Molekulare Botanik, Universität Ulm, 89069 Ulm, Germany.
The Journal of Biological Chemistry
|February 9, 2005
Summary
The ZiPD exosite, a unique protein region, is crucial for 3'-pre-tRNA processing by tRNase Z enzymes. This exosite is essential for recognizing pre-tRNA but not for the enzyme's catalytic activity.
Area of Science:
- Molecular Biology
- Enzymology
- Structural Biology
Background:
- Escherichia coli ZiPD is a model for 3 RNA processing endoribonucleases (tRNase Z) within the elaC gene family.
- Sequence analysis reveals a conserved ZiPD-specific exosite in functional homologs, absent in some tRNase Z classes.
Purpose of the Study:
- To investigate the function of the ZiPD exosite in pre-tRNA processing and substrate recognition.
- To determine the exosite's role in catalytic activity and dimerization.
Main Methods:
- Construction and characterization of a ZiPD variant lacking the exosite (ZiPDDelta).
- Assays for phosphodiesterase activity, substrate binding (gel shift), and pre-tRNA processing.
- Sequence alignment and comparison with known metallo-beta-lactamase domains.
Main Results:
- ZiPDDelta retained wild-type-like phosphodiesterase activity and dimerization.
- The exosite is not required for intrinsic catalytic activity or dimerization.
- ZiPDDelta failed to process pre-tRNA and bind mature tRNA, unlike wild-type ZiPD.
Conclusions:
- The ZiPD exosite is essential for pre-tRNA recognition, not for catalytic activity.
- This exosite guides physiological substrate recognition in the ZiPD/ElaC protein family.