Cloning and characterization of the gene encoding bdellin from Hirudo nipponia

Abstract

Bdellin is a potent trypsin, plamin and acrosin inhibitor purified from the leech. It is expressed in all parts of the body with high concentration in the reproductive organs.Bdellin-KL, bdellin from the Korean leech, has unsual hisitidine reach repeats which may be related to its function.But the physiological function in the leech has not revealed yet. To study on bdellin in gene level,the genomic clone encoding bdellin-KL was isolated from the constructed leech library.A positive clone containing the ORF which consists of 3 exons and 2 introns spanning about 1kb and 5``- and 3``- flanking region was isolated.The nucleotide sequences of exon-intron junctions were in agreement with the consensus 5``-GT …AG- 3``.To characterize the promoter, a transcription start point (tsp) was identified and the 5``-flanking sequence was analyzed.The consensus TATA box sequence (TATAAA) was found at - 28 bp from the tsp. Two CAAT boxes and two GC boxes were located upstream of the TATA box.Unusual ATA repeats were found upstream of the detected transcription factor binding sites.The promoter contained several putative cis-elements, which may serve as the binding sites of the important transcription factors related to the physiological function of bdellin.