Kevin Schey
Last active: 3/24/2020

Characterization of the major plasma protein of the eastern oyster, Crassostrea virginica, and a proposed role in host defense.

Itoh N, Xue QG, Schey KL, Li Y, Cooper RK, La Peyre JF
Comp Biochem Physiol B Biochem Mol Biol. 2011 158 (1): 9-22

PMID: 20601063 · DOI:10.1016/j.cbpb.2010.06.006

The major plasma protein of the eastern oyster, Crassostrea virginica, was purified, characterized and named dominin. SDS-PAGE analyses revealed that dominin consistently made up more than 40% of eastern oyster plasma and extrapallial fluid proteins. Three different forms of dominin were observed under non-reducing conditions. PCR and RACE primers designed from partial amino acid sequences obtained by tandem mass spectrometry of purified dominin identified 720bp of complete cDNA encoding 192 amino acid residues. Based on the deduced amino acid sequence of mature dominin, its molecular mass was calculated to be 19,389Da and was lower than the molecular mass of purified dominin measured by MALDI. This difference is likely due to post-translational modifications of dominin as the purified protein was found to be glycolysated, phosphorylated and likely sulfated. The amino acid sequence showed high similarity to the major plasma protein of the Pacific oyster (Crassostrea gigas), cavortin, and of the green-lipped mussel (Perna canaliculus), pernin, and to a recently described protein labeled as an extracellular superoxide dismutase from the Sydney rock oyster Saccostrea glomerata. While dominin was found to possess a Cu/Zn superoxide dismutase (SOD) domain, the domain was not completely conserved which explained why purified dominin lacked SOD activity. Dominin mRNA was detected in hemocytes by in situ hybridization and its expression measured by quantitative real time RT-PCR was significantly higher in winter than summer. Although the function(s) of dominin and homologous proteins is uncertain, the reported ability of cavortin to sequester iron and possibly limit the availability of this essential metal to pathogens suggests a potential role in host defense for this group of dominant plasma proteins. Other possible functions of dominin in antioxidation, wound repair, metal transport and shell mineralization are discussed leading us to conclude that dominin is likely a multifunctional protein.

Copyright © 2010 Elsevier Inc. All rights reserved.

MeSH Terms (11)

Amino Acid Sequence Animals Blood Proteins Crassostrea Electrophoresis, Polyacrylamide Gel In Situ Hybridization Molecular Sequence Data Reverse Transcriptase Polymerase Chain Reaction RNA, Messenger Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization Superoxide Dismutase

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