Cloning and Analysis of the Multiple Transcriptomes of Serine Protease Homologs in Crayfish ( Procambarus clarkii ).

Five different serine protease homologs (SPH) transcripts presumably or possibly resulting from alternative splicing were cloned from the hemocytes of crayfish ( Procambarus clarkii ) in this paper. Although different deletions of cDNA of SPH-2 and SPH-4 were found in the 5' untranslated regions, they shared the same open reading frame and encoded a 424 amino acids protein with a calculated molecular weight of 45.84 kDa compared with SPH-5 . The predicted cutting site of the signal peptide was located between Ala ²² and Glu ²³ ; a clip domain and a trypsin-like serine protease domain were located in the N-terminal and the C-terminal, respectively. Large deletions were found in the SPH-1 and SPH-3 . Both of them lacked the clip domain. The 22 amino acids signal peptide existed in the SPH-1 coding protein, and a low complexity region (LCR) was formed in the N-terminal of it. The deduced protein of SPH-1 contained 358 amino acids with a molecular weight of 38.80 kDa. There was only one trypsin-like serine protease domain found in the C-terminal of the SPH-3 coding protein. The deduced protein of SPH-3 contained 250 amino acids with a molecular weight of 26.90 kDa. The amino acid Ser (S) of the catalytic triad in trypsin-like serine protease domain of the proteins analyzed in this paper was replaced by Gly (G), suggesting that the SPH-1, SPH-2, SPH-3, SPH-4 , and SPH-5 were serine protease homologs.