title: Regulation of the ATPase activity of ABCE1 from Pyrococcus abyssi by Fe-S cluster status and Mg²⁺: implication for ribosomal function.
abstract: Ribosomal function is dependent on multiple proteins. The ABCE1 ATPase, a unique ABC superfamily member that bears two Fe₄S₄ clusters, is crucial for ribosomal biogenesis and recycling. Here, the ATPase activity of the Pyrococcus abyssi ABCE1 (PabABCE1) was studied using both apo- (without reconstituted Fe-S clusters) and holo- (with full complement of Fe-S clusters reconstituted post-purification) forms, and is shown to be jointly regulated by the status of Fe-S clusters and Mg²⁺. Typically ATPases require Mg²⁺, as is true for PabABCE1, but Mg²⁺ also acts as a negative allosteric effector that modulates ATP affinity of PabABCE1. Physiological [Mg²⁺] inhibits the PabABCE1 ATPase (K(i) of ∼1 μM) for both apo- and holo-PabABCE1. Comparative kinetic analysis of Mg²⁺ inhibition shows differences in degree of allosteric regulation between the apo- and holo-PabABCE1 where the apparent ATP K(m) of apo-PabABCE1 increases >30-fold from ∼30 μM to over 1 mM with M²⁺. This effect would significantly convert the ATPase activity of PabABCE1 from being independent of cellular energy charge (φ) to being dependent on φ with cellular [Mg²⁺]. These findings uncover intricate overlapping effects by both [Mg²⁺] and the status of Fe-S clusters that regulate ABCE1's ATPase activity with implications to ribosomal function.
authors.affiliation: Department of Chemistry, University of Central Florida, Orlando, FL 32816, USA.
authors.forename: Lynn M
authors.initials: LM
authors.lastname: Sims
authors.forename: Robert Y
authors.initials: RY
authors.lastname: Igarashi
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D006868:Hydrolysis; D007501:Iron; D008274:Magnesium / Q000494:pharmacology*; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D043903:Pyrococcus abyssi / Q000166:cytology* / Q000201:enzymology; D012270:Ribosomes / Q000378:metabolism*; D013455:Sulfur; D013696:Temperature
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D002614:Chelating Agents; D004533:Egtazic Acid; D000244:Adenosine Diphosphate; D013455:Sulfur; D000255:Adenosine Triphosphate; D004492:Edetic Acid; D007501:Iron; D000251:Adenosine Triphosphatases; D008274:Magnesium