Molecular characterization of the levansucrase gene from the endophytic sugarcane bacterium Acetobacter diazotrophicus SRT4.

摘要: The Acetobacter diazotrophicus SRT4 gene encoding levansucrase (EC 2.4.1.10) (IsdA) was isolated from a genomic library. nucleotide sequence of 2.3 kb DNA fragment sufficient for complementation levansucrase-deficient mutant (obtained by EMS treatment) determined. IsdA (1751 bp) coded polypeptide molecular mass 64.9 kDa with an isoelectric point 5.2. N-terminal amino acid the extracellular indicated presence precursor protein putative signal 51 residues which is possibly cleaved in two successive steps. Expression lac promoter Escherichia coli resulted production activity. deduced 48% and 46% identical levansucrases Gram-negative bacteria Zymomonas mobilis Erwinia amylovora, respectively, but only 28-31% Gram-positive bacteria. Multiple alignments published sequences revealed eight conserved motifs. A comparison catalytic properties A. those Bacillus subtilis suggested that one these motifs may be involved specificity synthesized product. Disruption genome lacking both activity ability to utilize sucrose as carbon source, suggesting key enzyme metabolism diazotrophicus.