title: The 17A structure of the 420 kDa lobster clottable protein by single particle reconstruction from cryoelectron micrographs.
abstract: Crustaceans form clots by the rapid crosslinking of a hemolymph clottable protein (CP) to form long, branched polymers. Clotting limits hemolymph loss from wounds as well as playing a part in the innate immune response. CP is a 420 kDa homodimer with a large quantity of associated lipid, primarily the carotenoid pigment astaxanthin. The three-dimensional structure of CP from the lobster Panulirus interruptus has been determined to 17 A resolution by single particle reconstruction from electron micrographs of the protein embedded in vitreous ice. The most prominent feature of this structure is a large cavity spanning the length of the molecule, which is the likely lipid binding pocket. The EM structure has been used in a low resolution molecular replacement search with data from orthorhombic CP crystals, and a solution is presented which describes the crystal packing.
authors.affiliation: Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093-0314, USA. jkollman@biomail.ucsd.edu
authors.forename: Justin M
authors.initials: JM
authors.lastname: Kollman
authors.forename: Joel
authors.initials: J
authors.lastname: Quispe
mesh_terms: D000818:Animals; D001777:Blood Coagulation; D001798:Blood Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D020285:Cryoelectron Microscopy; D018360:Crystallography, X-Ray; D019281:Dimerization; D006458:Hemolymph / Q000737:chemistry*; D021621:Imaging, Three-Dimensional; D008958:Models, Molecular; D008970:Molecular Weight; D016624:Negative Staining; D033521:Palinuridae / Q000737:chemistry*
chemical_list: D001798:Blood Proteins