6G1I

GH124 cellulase from Ruminiclostridium thermocellum in complex with Mn and fructosylated cellopentaose

Summary for 6G1I

• Entry DOI: 10.2210/pdb6g1i/pdb
• Related PRD ID: PRD_900011
• Descriptor: Glycosyl Hydrolase, beta-D-glucopyranose-(1-4)-beta-D-glucopyranose-(1-4)-beta-D-glucopyranose-(1-4)-beta-D-fructofuranose, beta-D-glucopyranose-(1-4)-beta-D-glucopyranose-(1-4)-beta-D-glucopyranose-(1-4)-beta-D-glucopyranose, ... (6 entities in total)
• Functional Keywords: metal binding, 2-oxohistidine, cellulase, hydrolase
• Biological source: Clostridium thermocellum (strain ATCC 27405 / DSM 1237 / NBRC 103400 / NCIMB 10682 / NRRL B-4536 / VPI 7372) (Ruminiclostridium thermocellum)
• Total number of polymer chains: 2
• Total formula weight: 53680.26

Authors

Urresti, S.,Davies, G.J.,Walton, P.H. (deposition date: 2018-03-21, release date: 2018-08-15, Last modification date: 2024-01-17)

Primary citation

Urresti, S.,Cartmell, A.,Liu, F.,Walton, P.H.,Davies, G.J.
Structural studies of the unusual metal-ion site of the GH124 endoglucanase from Ruminiclostridium thermocellum.
Acta Crystallogr F Struct Biol Commun, 74:496-505, 2018

PubMed Abstract: The recent discovery of `lytic' polysaccharide monooxygenases, copper-dependent enzymes for biomass degradation, has provided new impetus for the analysis of unusual metal-ion sites in carbohydrate-active enzymes. In this context, the CAZY family GH124 endoglucanase from Ruminiclostridium thermocellum contains an unusual metal-ion site, which was originally modelled as a Ca site but features aspartic acid, asparagine and two histidine imidazoles as coordinating residues, which are more consistent with a transition-metal binding environment. It was sought to analyse whether the GH124 metal-ion site might accommodate other metals. It is demonstrated through thermal unfolding experiments that this metal-ion site can accommodate a range of transition metals (Fe, Cu, Mn and Ni), whilst the three-dimensional structure and mass spectrometry show that one of the histidines is partially covalently modified and is present as a 2-oxohistidine residue; a feature that is rarely observed but that is believed to be involved in an `off-switch' to transition-metal binding. Atomic resolution (<1.1 Å) complexes define the metal-ion site and also reveal the binding of an unusual fructosylated oligosaccharide, which was presumably present as a contaminant in the cellohexaose used for crystallization. Although it has not been possible to detect a biological role for the unusual metal-ion site, this work highlights the need to study some of the many metal-ion sites in carbohydrate-active enzymes that have long been overlooked or previously mis-assigned.

PubMed: 30084399
DOI: 10.1107/S2053230X18006842

Experimental method

X-RAY DIFFRACTION (0.99 Å)