6SI8

Escherichia coli AGPase in complex with AMP.

Summary for 6SI8

• Entry DOI: 10.2210/pdb6si8/pdb
• EMDB information: 10208
• Descriptor: Glucose-1-phosphate adenylyltransferase, ADENOSINE MONOPHOSPHATE (2 entities in total)
• Functional Keywords: adp-glucose pyrophosphorilase complex with amp inhibitor, transferase
• Biological source: Escherichia coli
• Total number of polymer chains: 4
• Total formula weight: 196423.24

Authors

Cifuente, J.O.,Comino, N.,D'Angelo, C.,Marina, A.,Gil-Carton, D.,Albesa-Jove, D.,Guerin, M.E. (deposition date: 2019-08-09, release date: 2020-02-05, Last modification date: 2024-05-22)

Primary citation

Cifuente, J.O.,Comino, N.,D'Angelo, C.,Marina, A.,Gil-Carton, D.,Albesa-Jove, D.,Guerin, M.E.
The allosteric control mechanism of bacterial glycogen biosynthesis disclosed by cryoEM.
Curr Res Struct Biol, 2:89-103, 2020

PubMed Abstract: Glycogen and starch are the major carbon and energy reserve polysaccharides in nature, providing living organisms with a survival advantage. The evolution of the enzymatic machinery responsible for the biosynthesis and degradation of such polysaccharides, led the development of mechanisms to control the assembly and disassembly rate, to store and recover glucose according to cell energy demands. The tetrameric enzyme ADP-glucose pyrophosphorylase (AGPase) catalyzes and regulates the initial step in the biosynthesis of both α-polyglucans. AGPase displays cooperativity and allosteric regulation by sensing metabolites from the cell energy flux. The understanding of the allosteric signal transduction mechanisms in AGPase arises as a long-standing challenge. In this work, we disclose the cryoEM structures of the paradigmatic homotetrameric AGPase from (AGPase), in complex with either positive or negative physiological allosteric regulators, fructose-1,6-bisphosphate (FBP) and AMP respectively, both at 3.0 Å resolution. Strikingly, the structures reveal that FBP binds deeply into the allosteric cleft and overlaps the AMP site. As a consequence, FBP promotes a concerted conformational switch of a regulatory loop, RL2, from a "locked" to a "free" state, modulating ATP binding and activating the enzyme. This notion is strongly supported by our complementary biophysical and bioinformatics evidence, and a careful analysis of vast enzyme kinetics data on single-point mutants of AGPase. The cryoEM structures uncover the residue interaction networks (RIN) between the allosteric and the catalytic components of the enzyme, providing unique details on how the signaling information is transmitted across the tetramer, from which cooperativity emerges. Altogether, the conformational states visualized by cryoEM reveal the regulatory mechanism of AGPase, laying the foundations to understand the allosteric control of bacterial glycogen biosynthesis at the molecular level of detail.

PubMed: 34235472
DOI: 10.1016/j.crstbi.2020.04.005

Experimental method

ELECTRON MICROSCOPY (3.4 Å)