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Cryo-EM structure of the human GS-GN complex in the inhibited stateCryo-EM structure of the human GS-GN complex in the inhibited state
Structural highlights
DiseaseGYS1_HUMAN Glycogen storage disease due to muscle and heart glycogen synthase deficiency. The disease is caused by variants affecting the gene represented in this entry. FunctionGYS1_HUMAN Glycogen synthase participates in the glycogen biosynthetic process along with glycogenin and glycogen branching enzyme. Extends the primer composed of a few glucose units formed by glycogenin by adding new glucose units to it. In this context, glycogen synthase transfers the glycosyl residue from UDP-Glc to the non-reducing end of alpha-1,4-glucan.[1] Publication Abstract from PubMedGlycogen is the major glucose reserve in eukaryotes, and defects in glycogen metabolism and structure lead to disease. Glycogenesis involves interaction of glycogenin (GN) with glycogen synthase (GS), where GS is activated by glucose-6-phosphate (G6P) and inactivated by phosphorylation. We describe the 2.6 A resolution cryo-EM structure of phosphorylated human GS revealing an autoinhibited GS tetramer flanked by two GN dimers. Phosphorylated N- and C-termini from two GS protomers converge near the G6P-binding pocket and buttress against GS regulatory helices. This keeps GS in an inactive conformation mediated by phospho-Ser641 interactions with a composite "arginine cradle". Structure-guided mutagenesis perturbing interactions with phosphorylated tails led to increased basal/unstimulated GS activity. We propose that multivalent phosphorylation supports GS autoinhibition through interactions from a dynamic "spike" region, allowing a tuneable rheostat for regulating GS activity. This work therefore provides insights into glycogen synthesis regulation and facilitates studies of glycogen-related diseases. Mechanism of glycogen synthase inactivation and interaction with glycogenin.,Marr L, Biswas D, Daly LA, Browning C, Vial SCM, Maskell DP, Hudson C, Bertrand JA, Pollard J, Ranson NA, Khatter H, Eyers CE, Sakamoto K, Zeqiraj E Nat Commun. 2022 Jun 11;13(1):3372. doi: 10.1038/s41467-022-31109-6. PMID:35690592[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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