Structural and Functional Analysis of a Modified Glycolytic Pathway in Thermococcus litoralis: the Open and Closed Conformations of an ADP-dependent Glucokinase

摘要

ADP-dependent glucokinases (GKs) represent a unique kinase family within the phylogenetically diverse ribokinase superfamily that distinguish themselves from most other GKs (and from mainstream kinases in general) in their specific requirement for ADP, rather than ATP, as phosphate donor. First described in hyperthermophilic microorganisms in 1995 (1), today we know that ADP-dependent GKs are pervasive across the tree of life with representatives in mammals and human having been recently discovered (2). In the hyperthermophilic archeon Thermococcus litoralis, the ADP-dependent GK (77GK) phosphorylates D(+)-glucose (Glc) to D(+)-glucose-6-phosphate (G6P) in what constitutes the first step of a modified Embden-Meyerhof pathway. Besides its peculiar chemistry, 77GK presents sequence and structural features that afford optimal performance at temperatures near 90 °C. Previous kinetics and small X-ray scattering (SAXS) results from our groups suggest that the 77GK protein structure changes as substrates sequentially enter the active site from an open conformation (ligand-free state) through a semi-closed structure (Mg~(2+)·ADP) to finally a closed conformation (Mg~(2+)·ADP·Glc).