Allosteric activation unveils protein-mass modulation of ATP phosphoribosyltransferase product release

• Published in: Communications chemistry 2024-04, Vol.7 (1), p.77-77, Article 77
• Main Authors: Read, Benjamin J., Mitchell, John B. O., da Silva, Rafael G.
• Format: Article
• Language: English
• Subjects: 639/638/11/296; 639/638/45/173; 639/638/45/607/1167; Catalysis; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Enzymes; Low temperature; Proteins; Substitution reactions
• ISSN: 2399-3669; 2399-3669
• DOI: 10.1038/s42004-024-01165-8

Heavy-isotope substitution into enzymes slows down bond vibrations and may alter transition-state barrier crossing probability if this is coupled to fast protein motions. ATP phosphoribosyltransferase from Acinetobacter baumannii is a multi-protein complex where the regulatory protein HisZ allosterically enhances catalysis by the catalytic protein HisG S . This is accompanied by a shift in rate-limiting step from chemistry to product release. Here we report that isotope-labelling of HisG S has no effect on the nonactivated reaction, which involves negative activation heat capacity, while HisZ-activated HisG S catalytic rate decreases in a strictly mass-dependent fashion across five different HisG S masses, at low temperatures. Surprisingly, the effect is not linked to the chemical step, but to fast motions governing product release in the activated enzyme. Disruption of a specific enzyme-product interaction abolishes the isotope effects. Results highlight how altered protein mass perturbs allosterically modulated thermal motions relevant to the catalytic cycle beyond the chemical step. ATP phosphoribosyltransferase is a multi-protein complex where the catalytic protein HisGS is allosterically regulated by the regulatory protein HisZ; however, the protein dynamics of HisGS in enzyme catalysis remain underexplored. Here, the authors investigate the catalytic effect of isotope-labeled HisGS, revealing that the catalytic rate of HisZ-activated HisGS decreases in a mass-dependent fashion at low temperatures, which correlates to product release.