The catalytic power of magnesium chelatase: a benchmark for the AAA+ ATPases. Issue 12 (2nd June 2016)

• Record Type: Journal Article
• Authors: Adams, Nathan B. P.; Brindley, Amanda A.; Hunter, C. Neil; Reid, James D.
• Is Part Of: FEBS letters. Volume 590:Issue 12(2016)
• Page Start: 1687
• Page End: 1693
• Publication Date: 2016-06-02
• Subjects: ATP hydrolysis -- ATPases associated with various cellular activities (AAA) magnesium protoporphyrin IX -- chelatase -- chlorophyll biosynthesis -- Gun4; Biochemistry -- Periodicals; Biophysics -- Periodicals; Molecular biology -- Periodicals; Biochimie -- Périodiques; Biochemistry; Biophysics; Molecular biology; Periodicals; 572.05
• DOI: 10.1002/1873-3468.12214
• Languages: English
• ISSNs: 0014-5793

Abstract

Abstract : In the first committed reaction of chlorophyll biosynthesis, magnesium chelatase couples ATP hydrolysis to the thermodynamically unfavorable Mg 2+ insertion into protoporphyrin IX (ΔG°′ of circa 25–33 kJ·mol −1 ). We explored the thermodynamic constraints on magnesium chelatase and demonstrate the effect of nucleotide hydrolysis on both the reaction kinetics and thermodynamics. The enzyme produces a significant rate enhancement ( k cat / k uncat of 400 × 10 6 m ) and a catalytic rate enhancement, k cat / K m DIX K 0.5 Mg k uncat, of 30 × 10 15 m −1, increasing to 300 × 10 15 m −1 with the activator protein Gun4. This is the first demonstration of the thermodynamic benefit of ATP hydrolysis in the AAA + family. Abstract :