Abstract
ISLC3 is a member of IS3 family that is isolated from Lactobacillus casei. It has 1,351 bp and encodes for 382 amino acids. ISLC3 contains two open reading frames, named orfA and orfB, respectively. IS3 family can be found in both Gram positive and Gram negative bacteria genomes, and it replicates in a no conservative way. Transposon is a good mutagen that is related to DNA recombination or insertion of plasmid DNA into genome. Since it has an ability of reshaping the genome, it plays a critical role in evolutionary genetics. However, the recombination of genome with high frequent transposition can be a harm to the host, so the regulation of transposition is necessary. The integrase of retrovirus plays a role in insertion of reverse-transcripted cDNA into the target DNA in host genome,and the process of insertion is similar to transposition.The N terminal of IS3 family is relatively nonconserved, but all contain helix-turn-helix DNA binding domain. The catalytic core domain in C terminal contains the active site, DDE motif, function in linkage/terminal all catalytic reactions. The two residues, Asp and Glu, in the catalytic site are coupled to a divalent metal ion that is essential to its activity. I used a computer stimulation method with current theory, database and software InsightII, to constructed the molecular model of C terminal catalytic core domain of ISLC3. The molecular model of ISLC3 helps to study on the relationship between molecular structure and function in order to understandthe mechanism of ISLC3 transposition.