4HMZ

Crystal Structure of ChmJ, a 3'-monoepimerase from Streptomyces bikiniensis in complex with dTDP-quinovose

Summary for 4HMZ

• Entry DOI: 10.2210/pdb4hmz/pdb
• Related: 4HN0 4HN1
• Descriptor: Putative 3-epimerase in D-allose pathway, 1,2-ETHANEDIOL, [(2R,3S,5R)-3-hydroxy-5-(5-methyl-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)tetrahydrofuran-2-yl]methyl (2R,3R,4S,5S,6R)-3,4,5-trihydroxy-6-methyltetrahydro-2H-pyran-2-yl dihydrogen diphosphate, ... (4 entities in total)
• Functional Keywords: 3'-monoepimerase, natural product, deoxysugar, chalcomycin, dtdp-mycinose, dtdp-quinovose, cupin fold, nucleotide-linked sugar, epimerization, unknown function
• Biological source: Streptomyces bikiniensis
• Total number of polymer chains: 4
• Total formula weight: 91530.73

Authors

Holden, H.M.,Kubiak, R.L. (deposition date: 2012-10-18, release date: 2012-11-21, Last modification date: 2023-09-20)

Primary citation

Kubiak, R.L.,Phillips, R.K.,Zmudka, M.W.,Ahn, M.R.,Maka, E.M.,Pyeatt, G.L.,Roggensack, S.J.,Holden, H.M.
Structural and Functional Studies on a 3'-Epimerase Involved in the Biosynthesis of dTDP-6-deoxy-d-allose.
Biochemistry, 51:9375-9383, 2012

PubMed Abstract: Unusual deoxy sugars are often attached to natural products such as antibiotics, antifungals, and chemotherapeutic agents. One such sugar is mycinose, which has been found on the antibiotics chalcomycin and tylosin. An intermediate in the biosynthesis of mycinose is dTDP-6-deoxy-D-allose. Four enzymes are required for the production of dTDP-6-deoxy-D-allose in Streptomyces bikiniensis, a soil-dwelling microbe first isolated from the Bikini and Rongelap atolls. Here we describe a combined structural and functional study of the enzyme ChmJ, which reportedly catalyzes the third step in the pathway leading to dTDP-6-deoxy-D-allose formation. Specifically, it has been proposed that ChmJ is a 3'-epimerase that converts dTDP-4-keto-6-deoxyglucose to dTDP-4-keto-6-deoxyallose. This activity, however, has never been verified in vitro. As reported here, we demonstrate using (1)H nuclear magnetic resonance that ChmJ, indeed, functions as a 3'-epimerase. In addition, we determined the structure of ChmJ complexed with dTDP-quinovose to 2.0 Å resolution. The structure of ChmJ shows that it belongs to the well-characterized "cupin" superfamily. Two active site residues, His 60 and Tyr 130, were subsequently targeted for study via site-directed mutagenesis and kinetic analyses, and the three-dimensional architecture of the H60N/Y130F mutant protein was determined to 1.6 Å resolution. Finally, the structure of the apoenzyme was determined to 2.2 Å resolution. It has been previously suggested that the position of a conserved tyrosine, Tyr 130 in the case of ChmJ, determines whether an enzyme in this superfamily functions as a mono- or diepimerase. Our results indicate that the orientation of the tyrosine residue in ChmJ is a function of the ligand occupying the active site cleft.

PubMed: 23116432
DOI: 10.1021/bi3012737

Experimental method

X-RAY DIFFRACTION (2 Å)