Preliminary x-ray data on crystals of mandelate racemase.

D J Neidhart,V M Powers,G L Kenyon,A Y Tsou,S C Ransom,J A Gerlt,G A Petsko

doi:10.1016/s0021-9258(19)76534-x

Abstract

The recent development of a high-yield expression system and purification scheme for mandelate racemase has enabled us to produce sufficiently large quantities of pure enzyme to pursue x-ray crystallographic study. Large, single crystals of mandelate racemase have been grown from buffered polyethylene glycol (pH 8.0) in the presence of 10 mM magnesium chloride. The crystals grow in several habits, and we have identified two distinct tetragonal space groups in preliminary x-ray diffraction analysis. Crystals shaped as rectangular plates demonstrate 4/mmm Laue symmetry and systematic absences consistent with the space group I422. They have cell dimensions of a = b = 153 A and c = 181 A. Octahedrally shaped crystals of mandelate racemase display 4/m Laue symmetry and systematic absences consistent with the space group 14. Cell dimensions for these crystals are a = b = 113 A and c = 124 A. Based on estimates of Vm and on the measured density of the 1422 form, we suggest that two subunits of mandelate racemase (38,570 daltons/subunit) occupy the asymmetric unit in both crystal forms. Crystals of both forms diffract to beyond 3.0-A resolution. We are currently screening for isomorphous heavy-atom derivatives.

Highlights

The recent development of a high-yield expression system and purification scheme for mandelate racemase has enabledus to produce sufficiently large quantities of pureenzyme to pursue x-ray crystallographic study
Single crystals of mandelate racemase have been grown from buffered polyethylene glycolin the presence of 10 mM magnesium chloride
The crystals grow in several habits, and we have identified two distinct tetragonal space groups in preliminary x-ray diffraction analysis

Summary

Introduction

From the $Department of Chemistry, Massachusetts Instituteof Technology, Cambridge, Massachusetts 02139, the §Department of Pharmaceutical Chemistry, University of California, Sun Francisco, California94143, and the 11Department of Chemistry and Biochemistry, Universityof Maryland, College Park, Maryland20742 The recent development of a high-yield expression system and purification scheme for mandelate racemase has enabledus to produce sufficiently large quantities of pureenzyme to pursue x-ray crystallographic study. Single crystals of mandelate racemase have been grown from buffered polyethylene glycol (pH 8.0)in the presence of 10 mM magnesium chloride. The crystals grow in several habits, and we have identified two distinct tetragonal space groups in preliminary x-ray diffraction analysis.

Results

Conclusion