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

Shabelnikov S, Kiselev A - PLoS ONE (2015)

Bottom Line: 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.A combination of fold recognition algorithms and ab initio folding predicted that CRASP adopts an all-alpha, right-handed superhelical fold.CRASP is the first secretory protein expressed in molluscan atrium to be reported.

View Article: PubMed Central - PubMed

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.

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.

No MeSH data available.


The use of ab initio folding simulation to detect correct templates from a pool of structures identified by threading methods.(A) Top QUARK ab initio model refined with ModRefiner. The Cα-Cα′ distance restraints used to direct folding are satisfied (yellow). The C-terminal part of the protein shows four α-helices (blue) with right-handed superhelical topology. (B) Templates sorted according to an average TM-score calculated on the fold level, revealing SCOP a.118, an all-alpha right-handed superhelical fold (triangle). (C) Templates sorted according to the TM-score and the FATCAT p-value. A cluster of SCOP a.118.9 superfamily templates is evident (open triangles). Other templates from the SCOP a.118 fold (filled triangles) and other all-alpha templates (filled circles) are also shown.
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pone.0138787.g006: The use of ab initio folding simulation to detect correct templates from a pool of structures identified by threading methods.(A) Top QUARK ab initio model refined with ModRefiner. The Cα-Cα′ distance restraints used to direct folding are satisfied (yellow). The C-terminal part of the protein shows four α-helices (blue) with right-handed superhelical topology. (B) Templates sorted according to an average TM-score calculated on the fold level, revealing SCOP a.118, an all-alpha right-handed superhelical fold (triangle). (C) Templates sorted according to the TM-score and the FATCAT p-value. A cluster of SCOP a.118.9 superfamily templates is evident (open triangles). Other templates from the SCOP a.118 fold (filled triangles) and other all-alpha templates (filled circles) are also shown.

Mentions: The top model generated by QUARK is shown in Fig 6A (accession number PM0079929 in the Protein Model DataBase). The model had a seven-helix complex topology. Distance restraints derived from the disulphide bonding pattern were satisfied. Fig 6B shows the number of all-alpha templates grouped by SCOP fold level and plotted versus the average TM-score. The highest number of templates (24 hits) belonged to SCOP a.118, an all-alpha right-handed superhelical fold, with an average TM-score of 0.376. In Fig 6C, we plotted the FATCAT p-values of all-alpha templates versus the TM-scores. After sorting by the QUARK model, we found that the SCOP a.118.9 ENTH/VHS superfamily was clearly separated from the other all-alpha templates. The PDB IDs of these templates are 1DVP, 1ELK, 3LDZ, 1X5B, 3CLJ, 2DIW, 1SZA, 1SZ9, 2KM4 and 4FLB. The best match between the QUARK model and these templates was a group of four helices arranged in a right-handed superhelical fashion in the C-terminal region (Fig 6A). A representative threading alignment is shown in Fig 7. Remarkably, an alpha-hairpin formed by the sixth and seventh helices of the template matched to a long helix of CRASP that should form a similar super-secondary motif constrained by two enclosed disulphide bonds. This structural feature was recognized by threading programs and modelled by QUARK, allowing the assignment of the most favorable fold to CRASP.


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

Shabelnikov S, Kiselev A - PLoS ONE (2015)

The use of ab initio folding simulation to detect correct templates from a pool of structures identified by threading methods.(A) Top QUARK ab initio model refined with ModRefiner. The Cα-Cα′ distance restraints used to direct folding are satisfied (yellow). The C-terminal part of the protein shows four α-helices (blue) with right-handed superhelical topology. (B) Templates sorted according to an average TM-score calculated on the fold level, revealing SCOP a.118, an all-alpha right-handed superhelical fold (triangle). (C) Templates sorted according to the TM-score and the FATCAT p-value. A cluster of SCOP a.118.9 superfamily templates is evident (open triangles). Other templates from the SCOP a.118 fold (filled triangles) and other all-alpha templates (filled circles) are also shown.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4596865&req=5

pone.0138787.g006: The use of ab initio folding simulation to detect correct templates from a pool of structures identified by threading methods.(A) Top QUARK ab initio model refined with ModRefiner. The Cα-Cα′ distance restraints used to direct folding are satisfied (yellow). The C-terminal part of the protein shows four α-helices (blue) with right-handed superhelical topology. (B) Templates sorted according to an average TM-score calculated on the fold level, revealing SCOP a.118, an all-alpha right-handed superhelical fold (triangle). (C) Templates sorted according to the TM-score and the FATCAT p-value. A cluster of SCOP a.118.9 superfamily templates is evident (open triangles). Other templates from the SCOP a.118 fold (filled triangles) and other all-alpha templates (filled circles) are also shown.
Mentions: The top model generated by QUARK is shown in Fig 6A (accession number PM0079929 in the Protein Model DataBase). The model had a seven-helix complex topology. Distance restraints derived from the disulphide bonding pattern were satisfied. Fig 6B shows the number of all-alpha templates grouped by SCOP fold level and plotted versus the average TM-score. The highest number of templates (24 hits) belonged to SCOP a.118, an all-alpha right-handed superhelical fold, with an average TM-score of 0.376. In Fig 6C, we plotted the FATCAT p-values of all-alpha templates versus the TM-scores. After sorting by the QUARK model, we found that the SCOP a.118.9 ENTH/VHS superfamily was clearly separated from the other all-alpha templates. The PDB IDs of these templates are 1DVP, 1ELK, 3LDZ, 1X5B, 3CLJ, 2DIW, 1SZA, 1SZ9, 2KM4 and 4FLB. The best match between the QUARK model and these templates was a group of four helices arranged in a right-handed superhelical fashion in the C-terminal region (Fig 6A). A representative threading alignment is shown in Fig 7. Remarkably, an alpha-hairpin formed by the sixth and seventh helices of the template matched to a long helix of CRASP that should form a similar super-secondary motif constrained by two enclosed disulphide bonds. This structural feature was recognized by threading programs and modelled by QUARK, allowing the assignment of the most favorable fold to CRASP.

Bottom Line: 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.A combination of fold recognition algorithms and ab initio folding predicted that CRASP adopts an all-alpha, right-handed superhelical fold.CRASP is the first secretory protein expressed in molluscan atrium to be reported.

View Article: PubMed Central - PubMed

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.

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.

No MeSH data available.