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Protein & Peptide Letters


ISSN (Print): 0929-8665
ISSN (Online): 1875-5305

Extracellular Sunflower Proteins: Evidence on Non-classical Secretion of a Jacalin-Related Lectin

Author(s): Marcela Pinedo, Mariana Regente, Mercedes Elizalde, Ivana Y. Quiroga, Luciana A. Pagnussat, Jesus Jorrin-Novo, Ana Maldonado and Laura de la Canal

Volume 19, Issue 3, 2012

Page: [270 - 276] Pages: 7

DOI: 10.2174/092986612799363163


Extracellular proteins from sunflower seedlings were analyzed by electrophoresis followed by peptide mass fingerprinting. Tentative identification revealed novel proteins for this crop. A significant number of those proteins were not expected to be extracellular because they lacked the typical signal peptide responsible for secretion. In silico analysis showed that some members of this group presented the characteristic disordered structures of certain non-classical and leaderless mammalian secretory proteins. Among these proteins, a putative jacalin-related lectin (Helja) with a mannose binding domain was further isolated from extracellular fluids by mannose-affinity chromatography, thus validating its identification. Besides, immunolocalization assays confirmed its extracellular location. These results showed that a lectin, not predicted to be secreted in strict requirement of the N-terminal signal peptide, occurs in a sunflower extracellular compartment. The implications of this finding are discussed.

Keywords: Agglutinin, Helianthus annuus, jacalin, peptide mass fingerprinting, Secretome P, signal sequence, unconventional secretion, immunolocalization, In silico analysis, mannose-affinity chromatography

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