Cloning, Sequencing And Expression Of A Chitinase Gene From Aeromonas Caviae And Functional Disparity Between The Complete Chitinase And Its 563-aa Truncant

Aeromonas caviae can secrete several chintinases with different molecular weights. One chitinase gene chil has been cloned and sequenced. It encodes a protein of 865 amino acids with a signal peptide at the N-terminus,of which a polycystic-kidney-disease(PKD)-like domain,a triosephosphate-isomerase(TIM) catalytic region,a receptor-for-egg jelly(REJ)-like domain and two tandem chitin-binding-domains (ChBDs) locate from the N-to C-terminus. For up to 74.29% identity between the N-terminal 563 amino acids sequence of Chil and the crystallized Serratia marcenscens Chi A,it was possible to construct a partial SD-structure of Chi 1 by homology modeling. In order to illustrate the function of the rest 302 amino acids at the C-terminus,two pQE-70-derived recombinants were constructed to express the entire Chi 1 and its C-terminal truncant(Chi 1-). Chi 1 degraded colloidal chitin both endolytically and exolytically with JV-acetylglucosamine,chitobiose and chitotriose as its products while a C-teminal 302-amino-acid deleted mutant had its degrading pattern shift to chitobiose,chitotriose and chitotetraose. Further research showed a shifting of the minimal length of chitooligosaccharide needed for these two correlated proteins. In the case of full-length chitinase,it was chitotriose while with its truncated form,it turned out to be chitotetraose.