Download MendeleySignificance of the Protein Interface Configuration for Allostery in Imidazole Glycerol Phosphate Synthase.
Kneuttinger, A.C., Rajendran, C., Simeth, N.A., Bruckmann, A., Konig, B., Sterner, R.(2020) Biochemistry 59: 2729-2742
- PubMed: 32633500
- DOI: https://doi.org/10.1021/acs.biochem.0c00332
- Primary Citation of Related Structures:
6YMU - PubMed Abstract:
Imidazole glycerol phosphate synthase (ImGPS) from Thermotoga maritima is a model enzyme for studying allostery. The ImGPS complex consists of the cyclase subunit HisF and the glutaminase subunit HisH whose activity is stimulated by substrate binding to HisF in a V-type manner. To investigate the significance of a putative closing hinge motion at the cyclase:glutaminase interface for HisH activity, we replaced residue W123 in HisH with the light-switchable unnatural amino acid phenylalanine-4'-azobenzene (AzoF). Crystal structure analysis employing angle, buried surface area, and distance measurements showed that incorporation of AzoF at this position causes a closing of the interface by ∼18 ± 3%. This slightly different interface configuration results in a much higher catalytic efficiency in unstimulated HisH due to an elevated turnover number. Moreover, the catalytic efficiency of HisH when stimulated by binding of a substrate to HisF was also significantly increased by AzoF incorporation. This was caused by a K-type stimulation that led to a decrease in the apparent dissociation constant for its substrate, glutamine. In addition, AzoF improved the apparent binding of a substrate analogue at the HisF active site. Remarkably, light-induced isomerization of AzoF considerably enhanced these effects. In conclusion, our findings confirm that signal transduction from HisF to HisH in ImGPS involves the closing of the cyclase:glutaminase subunit interface and that incorporation of AzoF at a hinge position reinforces this catalytically relevant conformational change.
Organizational Affiliation:
Institute of Biophysics and Physical Biochemistry, Regensburg Center for Biochemistry, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany.
