6YMU

Imidazole Glycerol Phosphate Synthase

Summary for 6YMU

• Entry DOI: 10.2210/pdb6ymu/pdb
• Descriptor: Imidazole glycerol phosphate synthase subunit HisF, Imidazole glycerol phosphate synthase subunit HisH (3 entities in total)
• Functional Keywords: imidazole glycerol phosphate synthase, isomerase
• Biological source: Thermotoga maritima; More
• Total number of polymer chains: 6
• Total formula weight: 152854.57

Authors

Sterner, R.,Rajendran, C.,Andrea, K. (deposition date: 2020-04-09, release date: 2020-07-22, Last modification date: 2024-01-24)

Primary citation

Kneuttinger, A.C.,Rajendran, C.,Simeth, N.A.,Bruckmann, A.,Konig, B.,Sterner, R.
Significance of the Protein Interface Configuration for Allostery in Imidazole Glycerol Phosphate Synthase.
Biochemistry, 59:2729-2742, 2020

PubMed Abstract: Imidazole glycerol phosphate synthase (ImGPS) from 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.

PubMed: 32633500
DOI: 10.1021/acs.biochem.0c00332

Experimental method

X-RAY DIFFRACTION (2.11 Å)