Ca. Ocallaghan et al., PRODUCTION, CRYSTALLIZATION, AND PRELIMINARY-X-RAY ANALYSIS OF THE HUMAN MHC CLASS IB MOLECULE HLA-E, Protein science, 7(5), 1998, pp. 1264-1266
HLA-E is the first human class Ib major histocompatibility complex mol
ecule to be crystallized. HLA-E is highly conserved and almost nonpoly
morphic, and has recently been shown to be the first specialized ligan
d for natural killer cell receptors. In functional studies, HLA-E is u
nlike the class Ia MHC molecules in having tightly restricted peptide
binding specificity. HLA-E binds a limited set of almost identical lea
der sequence peptides derived from class Ia molecules and presents the
se at the cell surface for recognition by natural killer cell receptor
s. We now show that the extracellular region of HLA-E forms a stable c
omplex with beta 2 microglobulin and can be refolded around synthetic
peptide. Crystals of this complex formed slowly over four to six month
s in the presence of ammonium sulphate. The crystals diffract to 2.85
A with space group P3(1)21 and unit cell dimensions a = 182.2 Angstrom
, b = 182.2 Angstrom, c = 88.4 Angstrom.