PDBsum entry 2cis

Isomerase

PDB id: 2cis

Contents

Protein chain

288 a.a.

Ligands

TA6

Metals

_BA

Waters ×377

References listed in PDB file

Key reference

Title

Structure-Based functional annotation: yeast ymr099c codes for a d-Hexose-6-Phosphate mutarotase.

Authors

M.Graille, J.P.Baltaze, N.Leulliot, D.Liger, S.Quevillon-Cheruel, H.Van tilbeurgh.

Ref.

J Biol Chem, 2006, 281, 30175-30185. [DOI no: 10.1074/jbc.M604443200]

PubMed id

16857670

Abstract

Despite the generation of a large amount of sequence information over the last decade, more than 40% of well characterized enzymatic functions still lack associated protein sequences. Assigning protein sequences to documented biochemical functions is an interesting challenge. We illustrate here that structural genomics may be a reasonable approach in addressing these questions. We present the crystal structure of the Saccharomyces cerevisiae YMR099cp, a protein of unknown function. YMR099cp adopts the same fold as galactose mutarotase and shares the same catalytic machinery necessary for the interconversion of the alpha and beta anomers of galactose. The structure revealed the presence in the active site of a sulfate ion attached by an arginine clamp made by the side chain from two strictly conserved arginine residues. This sulfate is ideally positioned to mimic the phosphate group of hexose 6-phosphate. We have subsequently successfully demonstrated that YMR099cp is a hexose-6-phosphate mutarotase with broad substrate specificity. We solved high resolution structures of some substrate enzyme complexes, further confirming our functional hypothesis. The metabolic role of a hexose-6-phosphate mutarotase is discussed. This work illustrates that structural information has been crucial to assign YMR099cp to the orphan EC activity: hexose-phosphate mutarotase.

Figure 4.
Schematic representations of phosphosugars used in this study.

Figure 6.
Complexes of YMR099cp bound to hexose 6-phosphate sugars. Stereoview representation of Glc6P (A) and Tag6P (B) bound into the YMR099cp active site. The 2F[o] - F[c] electron density maps contoured at 1σ are shown in blue around the ligands. Hydrogen bonds made by the ligands with YMR099cp as well as Ba^2+ Tag6P oxygen coordination are depicted by red dashed lines. Water molecules are shown by red spheres.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2006, 281, 30175-30185) copyright 2006.