Standal R, Iversen T G, Coucheron D H, Fjaervik E, Blatny J M, Valla S
UNIGEN Center for Molecular Biology, University of Trondheim, Norway.
J Bacteriol. 1994 Feb;176(3):665-72. doi: 10.1128/jb.176.3.665-672.1994.
Recently, it was shown that a cellulose-negative mutant (Cel1) of Acetobacter xylinum ATCC 23769 carried an insertion of an indigenous transposable element (IS1031A) about 500 bp upstream of the bcs operon, required for cellulose synthesis. Here we show that Cel1 can be complemented by wild-type DNA covering the insertion point. Nucleotide sequencing of this region revealed the presence of two open reading frames, ORF1 and ORF2. ORF2, which is disrupted by the IS1031A insertion in Cel1, potentially encodes the complementing function. ORF1 encodes a protein (CMCax) with significant homology to previously described endoglucanases. A cloned DNA fragment containing ORF1 expressed a carboxymethyl cellulose-hydrolyzing activity in Escherichia coli. In A. xylinum, CMCax is secreted into the culture growth medium. The CMCax mature protein consists of 322 amino acids and has a molecular mass of 35.6 kDa.
最近研究表明，木醋杆菌ATCC 23769的纤维素阴性突变体（Cel1）在纤维素合成所需的bcs操纵子上游约500 bp处插入了一个内源转座元件（IS1031A）。在此我们表明，Cel1可以被覆盖插入点的野生型DNA互补。该区域的核苷酸测序揭示了两个开放阅读框ORF1和ORF2的存在。ORF2在Cel1中被IS1031A插入破坏，可能编码互补功能。ORF1编码一种与先前描述的内切葡聚糖酶具有显著同源性的蛋白质（CMCax）。一个含有ORF1的克隆DNA片段在大肠杆菌中表达了羧甲基纤维素水解活性。在木醋杆菌中，CMCax分泌到培养生长培养基中。CMCax成熟蛋白由322个氨基酸组成，分子量为35.6 kDa。
