1rwg
Crystal structure of Arthrobacter aurescens chondroitin AC lyase in complex with chondroitin tetrasaccharide
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OverviewOverview
Chondroitin lyases (EC 4.2.2.4 and EC 4.2.2.5) are, glycosaminoglycan-degrading enzymes that act as eliminases. Chondroitin, lyase AC from Arthrobacter aurescens (ArthroAC) is known to act on, chondroitin 4-sulfate and chondroitin 6-sulfate but not on dermatan, sulfate. Like other chondroitin AC lyases, it is capable of cleaving, hyaluronan. We have determined the three-dimensional crystal structure of, ArthroAC in its native form as well as in complex with its substrates, (chondroitin 4-sulfate tetrasaccharide, CS(tetra) and hyaluronan, tetrasaccharide) at resolution varying from 1.25 A to 1.9A. The primary, sequence of ArthroAC has not been previously determined but it was, possible to determine the amino acid sequence of this enzyme from the, high-resolution electron density maps and to confirm it by mass, spectrometry. The enzyme-substrate complexes were obtained by soaking the, substrate into the crystals for varying lengths of time (30 seconds to ten, hours) and flash-cooling the crystals. The electron density map for, crystals soaked in the substrate for as short as 30 seconds showed the, substrate clearly and indicated that the ring of central glucuronic acid, assumes a distorted boat conformation. This structure strongly supports, the lytic mechanism where Tyr242 acts as a general base that abstracts the, proton from the C5 position of glucuronic acid while Asn183 and His233, neutralize the charge on the glucuronate acidic group. Comparison of this, structure with that of chondroitinase AC from Flavobacterium heparinum, (FlavoAC) provides an explanation for the exolytic and endolytic mode of, action of ArthroAC and FlavoAC, respectively.
About this StructureAbout this Structure
1RWG is a Protein complex structure of sequences from Arthrobacter aurescens with NA and PO4 as ligands. Full crystallographic information is available from OCA.
ReferenceReference
High-resolution crystal structure of Arthrobacter aurescens chondroitin AC lyase: an enzyme-substrate complex defines the catalytic mechanism., Lunin VV, Li Y, Linhardt RJ, Miyazono H, Kyogashima M, Kaneko T, Bell AW, Cygler M, J Mol Biol. 2004 Mar 19;337(2):367-86. PMID:15003453
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