Purification and characterisation of a 48 kDa protein involved in the molting cycle of Penaeus monodon

Screening of crustacean proteins in relation to molting cycle revealed a 48 kDa protein which is cross reactive to Gas7 antibody and expressed predominantly in the intermolt stage where the cells remain quiescent. This 48 kDa protein of Penaeus monodon has been purified to homogeneity using ammonium sulphate precipitation, ion-exchange chromatography and electro elution. MALDI-TOF analysis of the purified protein revealed the presence of ANK repeat and LEM domain regions homologous to those of mouse. RT-PCR revealed 684 bp in all molting stages with varied expression. Bioinformatic analysis showed that the ankyrin repeat domain in the 48 kDa protein of P. monodon is highly conserved among Homo sapiens, Mus musculus, Rattus rattus, Danio rerio and Drosophila mojavensis. Secondary structure prediction revealed a commonly conserved region between mouse Gas7 and the ANK repeat region of P. monodon. Thus, we concluded that the isolated 48 kDa protein from P. monodon is a novel, Gas7-like protein with ANK repeat and LEM domain involved in molting.