Control of ATP hydrolysis by ADP bound at the catalytic site of chloroplast ATP synthase as related to protonmotive force and Mg sup 2+

Journal Article · Tue Jan 24 00:00:00 EST 1989 · Biochemistry; (USA)

DOI:https://doi.org/10.1021/bi00428a070· OSTI ID:5482305

Du, Z; Boyer, P D ^[1]

---

1. Univ. of California, Los Angeles (USA)

The activation of the ATP synthesis and hydrolysis capacity of isolated chloroplast membranes by protonmotive force is known to be associated with the release of tightly bound ADP from the ATP synthase. The data support the view that the activation requires only those structural changes occurring in the steady-state reaction mechanism. The trapping of ADP released during light activation or the chelation of Mg{sup 2+} with EDTA effectively reduces the rate of decay of the ATPase activity. When the release of tightly bound ADP and Mg{sup 2+} is promoted by light activation, followed by immediate dilution and washing to retard the rebinding of the ADP and Mg{sup 2+} released, the ATPase activity remains high in the dark long after the protonmotive force has disappeared. After the addition of ADP and Mg{sup 2+} the decay of the ATPase activity has the same characteristics as those of the unwashed chloroplast membrane. The results are interpreted as indicating that both Mg{sup 2+} and ADP must be present prior to exposure to MgATP for the ATPase to be inhibited. However, in contrast to the isolated chloroplast ATPase, the steady-state activity of the membrane-bound ATPase is not inhibited by excess Mg{sup 2+}. The replacement of ({sup 3}H)ADP from catalytic sites during hydrolysis of unlabeled ATP or during photophosphorylation with unlabeled ADP occurs as anticipated if Mg{sup 2+} and ADP bound at one catalytic site without P{sub i} block catalysis by all three enzyme sites. The inhibited form induced by Mg{sup 2+} and ADP may occur only under laboratory conditions and not have an in vivo role.

• DOE Contract Number: FG03-88ER13845
• OSTI ID: 5482305
• Journal Information: Biochemistry; (USA), Vol. 28:2; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ATP
ENZYMATIC HYDROLYSIS
ATP-ASE
ENZYME INDUCTION
ADP
CATIONS
CHLOROPLASTS
ENZYME ACTIVITY
MAGNESIUM COMPOUNDS
TRITIUM COMPOUNDS
VISIBLE RADIATION
ACID ANHYDRASES
ALKALINE EARTH METAL COMPOUNDS
CELL CONSTITUENTS
CHARGED PARTICLES
CHEMICAL REACTIONS
DECOMPOSITION
ELECTROMAGNETIC RADIATION
ENZYMES
GENE REGULATION
HYDROGEN COMPOUNDS
HYDROLASES
HYDROLYSIS
IONS
LYSIS
NUCLEOTIDES
ORGANIC COMPOUNDS
PHOSPHOHYDROLASES
RADIATIONS
SOLVOLYSIS
550201* - Biochemistry- Tracer Techniques