Wang W Y, Thomson J A
Department of Microbiology, University of Cape Town, Rondebosch, South Africa.
Mol Gen Genet. 1990 Jul;222(2-3):265-9. doi: 10.1007/BF00633827.
The nucleotide sequence of a 3.6 kb DNA fragment containing a cellodextrinase gene (celA) from Ruminococcus flavefaciens FD-1 was determined. The gene was expressed from its own regulatory region in Escherichia coli and a putative consensus promoter sequence was identified upstream of a ribosome binding site and a TTG start codon. The complete amino acid sequence of the CelA enzyme (352 residues) was deduced and showed no significant homology to cellulases from other organisms. Two lysozyme-type active sites were found in the amino-terminal third of the enzyme. In E. coli the cloned Cel A protein was translocated into the periplasm. The lack of a typical signal sequence, and the results of transposon phoA mutagenesis experiments indicated that CelA is secreted by a mechanism other than a leader peptide.
测定了来自黄化瘤胃球菌FD-1的一个包含纤维糊精酶基因（celA）的3.6 kb DNA片段的核苷酸序列。该基因在大肠杆菌中从其自身的调控区域表达，并且在核糖体结合位点和TTG起始密码子上游鉴定出一个假定的共有启动子序列。推导了CelA酶的完整氨基酸序列（352个残基），并且该序列与其他生物体的纤维素酶没有显著同源性。在该酶氨基端的三分之一区域发现了两个溶菌酶型活性位点。在大肠杆菌中，克隆的CelA蛋白被转运到周质空间。缺乏典型的信号序列以及转座子phoA诱变实验的结果表明，CelA是通过一种不同于前导肽的机制分泌的。
