Abstract:
An antimicrobial protein, crustin, is involved in the innate immunity of crustacean by defending the host directly against the microbial pathogens. By data mining the Penaeus monodon EST database, two type I crustins, carcinin. Pm1 and 2, and ten type II crustins, crustin. Pm1-10, were identified. The abundant crustins were crustin. Pm1, 4 and 7, each with variation in the length of Gly-rich repeat among its members. A few crustin. Pm1, 4 and 7 with deletion in the Cys-rich region were also observed. Furthermore, the crustin. Pm4 with the longest N-terminal Gly-rich region was characterized. The crustinPm4 allelic genes were expressed mainly from the hemocytes. Its expression was up-regulated readily by WSSV infection and gradually decreased to normal level afterwards. The recombinant crustin. Pm4-1 (rcrustin. Pm4-1) isoform was produced using the Escherichia coli expression system and tested for its antimicrobial activity. The rcrustin. Pm4-1 was able to inhibit the growth of a Gram-positive bacterium, Bacillus megaterium but not Bacillus subtilis, Micrococcus luteus and Staphylococcus aureus. It also inhibited the growth of two Gram-negative bacteria, E. coli 363 and Vibrio harveyi 639 at lower potency. The rcrustin. Pm4-1 affected the WSSV infection because the expression of an intermediate early gene ie1 in WSSV-infected hemocyte cell culture was reduced. It was shown further that the rcrustin. Pm4-1 could delay by about one and a half days the manifestation of disease by WSSV. © 2014 Elsevier Ltd.