High expression of a novel leucine-rich repeat protein in hemocytes and the lymphoid organ of the black tiger shrimp Penaeus monodon

Abstract

A novel leucine-rich repeat (LRR) cDNA has been cloned from hemocytes of the black tiger shrimp Penaeus monodon by 5′ rapid amplification of cDNA ends. The full-length of P. monodon LRR (PmLRR) consisted of 2604 bp with a 1686-bp open reading frame, encoding 561 amino acids. The deduced protein contained a high proportion of leucine residues (17%) and had significant homology to LRR-containing proteins from bacteria to humans. Sixteen tandem LRR motifs of 23-24 amino acids in length occurred in the primary sequence. The computed 3D structure revealed a horseshoe shape consisting of alternately repeated strand and helical domains. Such structures are generally considered to mediate protein-protein interactions and to our knowledge, this is the first report of an LRR protein from a crustacean. PmLRR expression was tissue-specific (i.e. highest in hemocytes, intestine and lymphoid organ) suggesting that it may play some roles in shrimp defense against pathogens. A preliminary test suggested that PmLRR may be down-regulated after viral injection. © 2006 Elsevier Ltd. All rights reserved.