Regulation of Leishmania major PAS domain‐containing phosphoglycerate kinase by cofactor Mg2+ ion at neutral pH
Open Access
- 20 March 2020
- journal article
- research article
- Published by Wiley in The FEBS Journal
- Vol. 287 (23), 5183-5195
- https://doi.org/10.1111/febs.15305
Abstract
Recently, we described the PAS domain‐containing phosphoglycerate kinase from Leishmania major (LmPAS‐PGK) that shows acidic pH (5.5)‐dependent optimum catalytic activity. The PAS domain of LmPAS‐PGK is expected to regulate phosphoglycerate kinase (PGK) activity during catalysis, but the mechanism of regulation by PAS domain at the molecular level is uncharacterized. In this work, we have utilized the full length, PAS domain‐deleted and mutant enzymes to measure the enzymatic activity in the presence of divalent cation at various pH. Catalytic activity measurement indicates that Mg2+ binding through PAS domain inhibits the PGK activity at pH 7.5 and this inhibition is withdrawn at pH 5.5. To identify the Mg2+ binding residues of the PAS domain, we exploited a systematic mutational analysis of all (four) His residues in the PAS domain for potential divalent cation binding. Replacement of His‐57 with alanine resulted in depression in the presence of Mg2+ at pH 7.5, but H71A, H89A and H111A showed similar characteristics with respect to the wild‐type protein. Fluorescence and isothermal titration calorimetry (ITC) studies revealed that H57 is responsible for Mg2+ binding in the absence of substrates. Thus, the protonated form of His57 at acidic pH 5.5 destabilizes the Mg2+ binding in the PAS domain, which is an essential requirement in the wild‐type LmPAS‐PGK for a conformational alteration in the sensor domain that, sequentially, activates the phosphoglycerate kinase domain, resulting in the synthesis of higher amounts of ATP.Keywords
Funding Information
- Department of Science and Technology, India (EMR/2016/001415)
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