Evidence indicating the existence of a novel family of serine protease inhibitors that may be involved in marine invertebrate immunity
Document Type
Article
Publication Date
1-1-2009
Abstract
A new serine protease inhibitor, designated cvSI-2, was purified and characterized from the plasma of the eastern oyster, Crassostrea virginica. CvSI-2 inhibited the serine protease subtilisin A in a slow-tight binding manner, with an overall dissociation constant Ki* of 0.18 nM. It also inhibited perkinsin, the major extracellular protease of the oyster protozoan parasite Perkinsus marinus. Sequencing of cvSI-2 cloned cDNA revealed an open reading frame of 258 bp encoding a polypeptide of 85 amino acids, with the 18 N-terminal amino acids forming a signal peptide. The mature cvSI-2 molecule predicted consisted of 67 amino acids with 12 cysteine residues and a calculated molecular mass of 7202.96 Da. Overall 91% of the cvSI-2 amino acid sequence predicted from cDNA was confirmed by tandem mass spectrometry sequencing of purified cvSI-2. In addition, serine 43 and a threonine substitution at this position were observed. CvSI-2 amino acid sequence showed a 38% identity and 54% similarity with that of cvSI-1, the first protease inhibitor purified and characterized from a bivalve mollusc. Like cvSI-1, cvSI-2 gene was expressed in the basophil cells of digestive tubules. BLAST search found multiple ESTs from the eastern oyster, Pacific oyster, Mediterranean mussel, and sea vase, a tunicate, which could encode proteins with sequences similar to cvSI-1 and cvSI-2. Our findings indicate that cvSI-1 and cvSI-2 are members of a novel family of serine protease inhibitors in bivalve molluscs and perhaps other marine invertebrates, which share the characteristic cysteine array C-X4-9-C-X4-6-C-X7-C-X4-C-T-C-X6-9-C-X5-C-X3-7-C-X6-10-C-X4-C-X-C. © 2009 Elsevier Ltd. All rights reserved.
Publication Source (Journal or Book title)
Fish and Shellfish Immunology
First Page
250
Last Page
259
Recommended Citation
Xue, Q., Itoh, N., Schey, K., Cooper, R., & La Peyre, J. (2009). Evidence indicating the existence of a novel family of serine protease inhibitors that may be involved in marine invertebrate immunity. Fish and Shellfish Immunology, 27 (2), 250-259. https://doi.org/10.1016/j.fsi.2009.05.006