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Characterization and immunolocalization of a main proteinaceous component of the cell wall of the protozoan parasite Perkinsus atlanticus

J. F.  MONTES  a1 a2 c1 , M.  DURFORT  a1 a2 , A.  LLADÓ  a1 and J.  GARCÍA-VALERO  a1 a2 a1 Departament de Biologia Cel·lular, Facultat de Biologia, Universitat de Barcelona, Avda. Diagonal 645, E-08028 Barcelona, Spain a2 Centre de Referència de Recerca i Desenvolupament en Aqüicultura de la Generalitat de Catalunya, CRAC

Article author query montes j     durfort m     lladÓ a     garcÍa-valero j

Abstract

Described in the present study is a major component of the cell wall of 2 of the most pathogenic parasites of molluscs, Perkinsus atlanticus and P. marinus. The component is a high molecular weight protein (233 kDa), which we have named PWP-1 (for Perkinsus wall protein-1). Western blots, using a polyclonal serum generated against purified PWP-1 from P. atlanticus, revealed that this protein is expressed by all walled developmental stages of this protozoon. By means of immunogold electron microscopy, labelling for PWP-1 was strong and specifically associated with the cell wall. The label density and distribution pattern was quite different between trophozoites and prezoosporangia. With regard to the structural organization of this protein, PWP-1 is disulphide-linked to other cell wall components and released from the cell wall only following treatment with a sulphydryl agent. We also report that PWP-1 is a trypsin-resistant protein, both in its native and heat-denatured conformation. In addition, results from the N-terminal microsequence of this protein allow us to define PWP-1 as a novel cell wall protein. Overall, our findings strongly suggest that PWP-1 plays a key role in the organization of the cell wall of these protozoa, promoting their survival.