Open AccessCrystallization and preliminary characterization of three different crystal forms of human saposin C heterologously expressed in Pichia pastoris
Author(s) -
SchultzHeienbrok Robert,
Remmel Natascha,
Klingenstein R.,
Rossocha Maksim,
Sandhoff Konrad,
Saenger Wolfram,
Maier Timm
Publication year - 2006
Publication title -
acta crystallographica section f
Language(s) - English
Resource type - Journals
ISSN - 1744-3091
DOI - 10.1107/s1744309105043186
Subject(s) - pichia pastoris , molecular replacement , orthorhombic crystal system , crystallization , molecule , crystallography , chemistry , protein crystallization , recombinant dna , crystal structure , biochemistry , organic chemistry , gene
The amphiphilic saposin proteins (A, B, C and D) act at the lipid–water interface in lysosomes, mediating the hydrolysis of membrane building blocks by water‐soluble exohydrolases. Human saposin C activates glucocerebrosidase and β‐galactosylceramidase. The protein has been expressed in Pichia pastoris , purified and crystallized in three different crystal forms, diffracting to a maximum resolution of 2.5 Å. Hexagonal crystals grew from 2‐propanol‐containing solution and contain a single molecule in the asymmetric unit according to the Matthews coefficient. Orthorhombic and tetragonal crystals were both obtained with pentaerythritol ethoxylate and are predicted to contain two molecules in the asymmetric unit. Attempts to determine the respective crystal structures by molecular replacement using either the known NMR structure of human saposin C or a related crystal structure as search models have so far failed. The failure of the molecular‐replacement method is attributed to conformational changes of the protein, which are known to be required for its biological activity. Crystal structures of human saposin C therefore might be the key to mapping out the conformational trajectory of saposin‐like proteins.