New Crystal Forms of the Motile Major Sperm Protein (MSP) ofAscaris suum

2.5 Å Resolution Crystal Structure of the Motile Major Sperm Protein (MSP) ofAscaris suum

“…In two instances, a strand switches from one sheet to the other as a result of a kink introduced by a cis-proline residue (proline residues 13 and 57). Hydrophobic side-chains from adjacent faces of the (Bullock et al, 1996) and PapD (Holmgren & Branden, 1989) produced from superimposing the three-dimensional structures of each molecule. Insertions and deletions were made to match the pattern of strands in each and the set of residues that had a RMS displacement of less than 1 Å between the two structures are shown in bold.…”

“…Bacterially expressed a-MSP was purified and crystallized as described (Bullock et al, 1996). Previous studies have shown that these crystals contain two MSP polypeptide chains per asymmetric unit.…”

“…Ascaris a-MSP cDNA was expressed in Escherichia coli using the T7 based system (Studier et al, 1990) as described in detail by Bullock et al (1996). Briefly, Ascaris a-MSP cDNA in pET11d was transformed into BL21(DE3) cells and grown overnight at 34°C in 2 × TY medium containing 50 mg/ml ampicillin.…”

“…Both native and bacterially expressed MSP dimerize strongly in solution over a broad range of conditions (Haaf et al, 1996). Both native MSP isoforms as well as bacterially expressed material can be induced to form filaments in vitro that are indistinguishable from native filaments (King et al, 1992Bullock et al, 1996). Furthermore, electron microscopy and image processing have demonstrated that these filaments are constructed from two subfilaments wound around one another in a helix of pitch 225 Å .…”

“…Unfortunately, the extremely long unit cell of these crystals coupled with their high mosaic spread and the large (probably 16) number of MSP units in the asymmetric unit have frustrated attempts to solve the structure to atomic resolution. However, we recently obtained two new crystal forms of MSP that contained many fewer polypeptide chains in the asymmetric unit (Bullock et al, 1996) and which are suitable for high-resolution structural investigation by X-ray crystallography.…”