title: Cysteine-Rich Atrial Secretory Protein from the Snail Achatina achatina: Purification and Structural Characterization.
abstract: Despite extensive studies of cardiac bioactive peptides and their functions in molluscs, soluble proteins expressed in the heart and secreted into the circulation have not yet been reported. In this study, we describe an 18.1-kDa, cysteine-rich atrial secretory protein (CRASP) isolated from the terrestrial snail Achatina achatina that has no detectable sequence similarity to any known protein or nucleotide sequence. CRASP is an acidic, 158-residue, N-glycosylated protein composed of eight alpha-helical segments stabilized with five disulphide bonds. A combination of fold recognition algorithms and ab initio folding predicted that CRASP adopts an all-alpha, right-handed superhelical fold. CRASP is most strongly expressed in the atrium in secretory atrial granular cells, and substantial amounts of CRASP are released from the heart upon nerve stimulation. CRASP is detected in the haemolymph of intact animals at nanomolar concentrations. CRASP is the first secretory protein expressed in molluscan atrium to be reported. We propose that CRASP is an example of a taxonomically restricted gene that might be responsible for adaptations specific for terrestrial pulmonates.
authors.affiliation: Department of Cytology and Histology, Saint-Petersburg State University, St. Petersburg, Russia; Laboratory of Cell Morphology, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia.
authors.forename: Sergey
authors.initials: S
authors.lastname: Shabelnikov
authors.affiliation: Laboratory of Cell Morphology, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia; Institute of Molecular Biology and Genetics, Almazov Federal Medical Research Centre, St. Petersburg, Russia.
authors.forename: Artem
authors.initials: A
authors.lastname: Kiselev
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003545:Cysteine / Q000737:chemistry* / Q000378:metabolism*; D006325:Heart Atria / Q000378:metabolism*; D006458:Hemolymph / Q000378:metabolism; D008974:Mollusca / Q000378:metabolism; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism*; D012908:Snails / Q000378:metabolism*
chemical_list: D011506:Proteins; D003545:Cysteine