Crystallization of a Golgi-associated PR-1-related protein (GAPR-1) that localizes to lipid-enriched microdomains

The human Golgi-associated PR-1-related protein (GAPR-1) is closely related to plant pathogenesis-related (PR-1) proteins, which are upregulated in response to pathogen attack. Family members have been identified in a variety of organisms, together constituting the superfamily of PR-1 proteins. GAPR-1 is found within lipid-enriched microdomains on the cytosolic side of the endomembrane system. GAPR-1 is tightly anchored to membranes and absent from the cytosol, although it does not possess a membrane-spanning domain. Crystals of recombinantly expressed GAPR-1 have been grown that diffract to high (1.5 Å) resolution. Complete data sets have been collected on a trigonal crystal form (P3₁21/P3₂21), with unit-cell parameters a = b = 73.5, c = 63.2 Å. Molecular replacement using the NMR coordinates of tomato pathogenesis-related protein (28% identity) was unsuccessful and a search for heavy-metal derivatives or alternative phasing methods has been initiated.