乳酸菌产蛋白酶基因的克隆.pdf

Gene 495 (2012) 154–162
Contents lists available at SciVerse ScienceDising the gene library con-
Levanase
structed in the E. coli system. The levH1 gene encoded a protein (designated as LevH1), of which calculated
Inulinase
β-propeller molecular mass and pI were -kDa and , respectively. LevH1 (1296 amino-acids long) was predicted
β-sandwich to have a four-domain structure, containing (i) an N-terminal secretion signal of 40 amino-acids, (ii) variable
Lactobacillus casei domain of about 140 residues whose function is unclear, (iii) a catalytic domain of about 630 residues with
glycoside-hydrolase activity consisting of two modules, a five-blade β-propeller module linked to a β-
sandwich module, (iv) a C-terminal domain of about 490 residues comprising five nearly perfect repeat se-
quences of 80 residues homologous to equivalents of other hypothetical cell surface proteins, followed by
37-residues rich in Ser/Thr/Pro/Gly, a pentad LPQAG (the LPXTG homologue). When overproduced in E.