title: Structure/function analysis of spinalin, a spine protein of Hydra nematocysts.
abstract: The nematocyst capsules of the cnidarians are specialized explosive organelles that withstand high osmotic pressures of approximately 15 MPa (150 bar). A tight disulfide network involving cysteine-rich capsule wall proteins, like minicollagens and nematocyst outer wall antigen, characterizes their molecular composition. Nematocyst discharge leads to the expulsion of a long inverted tubule that was coiled inside the capsule matrix before activation. Spinalin has been characterized as a glycine-rich, histidine-rich protein associated with spine structures on the surface of everted tubules. Here, we show that full-length Hydra spinalin can be expressed recombinantly in HEK293 cells and has the property to form disulfide-linked oligomers, reflecting its state in mature capsules. Furthermore, spinalin showed a high tendency to associate into dimers in vitro and in vivo. Our data, which show incomplete disulfide connectivity in recombinant spinalin, suggest a possible mechanism by which the spine structure may be linked to the overall capsule polymer.
authors.affiliation: Department of Biophysical Chemistry, Biozentrum, University of Basel, Switzerland.
authors.forename: Simon
authors.initials: S
authors.lastname: Hellstern
authors.forename: Jörg
authors.initials: J
authors.lastname: Stetefeld
authors.forename: Charlotte
authors.initials: C
authors.lastname: Fauser
authors.forename: Ariel
authors.initials: A
authors.lastname: Lustig
authors.forename: Jürgen
authors.initials: J
authors.lastname: Engel
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Holstein
authors.forename: Suat
authors.initials: S
authors.lastname: Ozbek
mesh_terms: D000818:Animals; D002460:Cell Line; D002942:Circular Dichroism; D019281:Dimerization; D004220:Disulfides / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D006829:Hydra / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D015388:Organelles / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D017433:Protein Structure, Secondary; D011506:Proteins / Q000032:analysis* / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism / Q000648:ultrastructure; D013329:Structure-Activity Relationship; D014461:Ultracentrifugation
chemical_list: D004220:Disulfides; D011506:Proteins; D011994:Recombinant Proteins; C113263:spinalin