Cysteine-Rich Atrial Secretory Protein from the Snail Achatina achatina: Purification and Structural Characterization

PLoS One. 2015 Oct 7;10(10):e0138787. doi: 10.1371/journal.pone.0138787. eCollection 2015.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cysteine / chemistry*
  • Cysteine / metabolism*
  • Heart Atria / metabolism*
  • Hemolymph / metabolism
  • Mollusca / metabolism
  • Protein Conformation
  • Proteins / chemistry*
  • Proteins / metabolism*
  • Snails / metabolism*

Substances

  • Proteins
  • Cysteine

Grants and funding

The authors acknowledge Saint-Petersburg State University (http://eng.spbu.ru/) for a research grant 1.50.1042.2014; Russian Foundation for Basic Research (http://www.rfbr.ru/rffi/eng) for a research grant 11-04-00400a to SS; and Russian Science Foundation for a research grant 15-15- 20026 (http://rscf.ru/en/). The protein sequencing costs were covered by grant from Dynasty Foundation (http://www.dynastyfdn.com/english/) to SS. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.