Genetic organization of the cellulose synthase operon in Acetobacter xylinum.
Genetic organization of the cellulose synthase operon in Acetobacter xylinum.
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DOI：
10.1073/pnas.87.20.8130
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发表时间：
1990-10
影响因子：
11.1
通讯作者：
Hing C. Wong;Anna Lisa Fear;Roger D. CALHOONt;Gregory H. Eichinger;Raphael Mayer;Dorit Amikam;Moshe Benziman;David H. Gelfand;J. H. Meade;W. Anne;Emerick;Robert Bruner;Arie BEN-BASSAT;R. Tal
中科院分区：
文献类型：
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作者：
Hing C. Wong;Anna Lisa Fear;Roger D. CALHOONt;Gregory H. Eichinger;Raphael Mayer;Dorit Amikam;Moshe Benziman;David H. Gelfand;J. H. Meade;W. Anne;Emerick;Robert Bruner;Arie BEN-BASSAT;R. Tal
通过与缺乏纤维素合成酶活性的菌株进行遗传互补，分离到一个操纵子，该操纵子编码细菌纤维素合成（bcs）所需的4个蛋白。核苷酸序列分析表明，纤维素合成酶操纵子长9217个碱基对，由四个基因组成。这四个基因-bcsA，bcsB，bcsC和bcsD-似乎是间接耦合和转录为多顺反子mRNA的起始位点97个碱基的编码区的第一个基因（bcsA）的操纵子上游。遗传互补测试和基因破坏分析的结果表明，操纵子中的所有四个基因都是A中最大细菌纤维素合成所需的。木纤维由bcsA、bcsB、bcsC和bcsD编码的蛋白质的计算分子量分别为84.4、85.3、141.0和17.3 kDa。操纵子中的第二个基因（bcsB）编码纤维素合酶的催化亚基。bcsA、bcsC和bcsD基因产物的功能尚不清楚。在bcsA基因座突变的细菌菌株被发现是由于缺乏纤维素合成酶和二鸟苷酸环化酶的活动，在纤维素合成不足。突变体的bcsC和bcsD基因在体内纤维素生产受损，即使他们有能力使所有必要的代谢前体和环二鸟苷酸，纤维素合成酶的激活剂，并表现出纤维素合成酶活性在体外。当整个操纵子存在于细菌细胞中的多拷贝质粒上时，纤维素合酶活性和纤维素生物合成都增加。当纤维素合成酶操纵子的启动子在染色体上被E. coli tac或lac启动子，纤维素产量降低，同时纤维素合成酶活性降低。这些观察结果表明，bcs操纵子的表达是限速纤维素合成在A。木纤维
An operon encoding four proteins required for bacterial cellulose biosynthesis (bcs) in Acetobacter xylinum was isolated via genetic complementation with strains lacking cellulose synthase activity. Nucleotide sequence analysis indicated that the cellulose synthase operon is 9217 base pairs long and consists of four genes. The four genes--bcsA, bcsB, bcsC, and bcsD--appear to be translationally coupled and transcribed as a polycistronic mRNA with an initiation site 97 bases upstream of the coding region of the first gene (bcsA) in the operon. Results from genetic complementation tests and gene disruption analyses demonstrate that all four genes in the operon are required for maximal bacterial cellulose synthesis in A. xylinum. The calculated molecular masses of the proteins encoded by bcsA, bcsB, bcsC, and bcsD are 84.4, 85.3, 141.0, and 17.3 kDa, respectively. The second gene in the operon (bcsB) encodes the catalytic subunit of cellulose synthase. The functions of the bcsA, bcsC, and bcsD gene products are unknown. Bacterial strains mutated in the bcsA locus were found to be deficient in cellulose synthesis due to the lack of cellulose synthase and diguanylate cyclase activities. Mutants in the bcsC and bcsD genes were impaired in cellulose production in vivo, even though they had the capacity to make all the necessary metabolic precursors and cyclic diguanylic acid, the activator of cellulose synthase, and exhibit cellulose synthase activity in vitro. When the entire operon was present on a multicopy plasmid in the bacterial cell, both cellulose synthase activity and cellulose biosynthesis increased. When the promoter of the cellulose synthase operon was replaced on the chromosome by E. coli tac or lac promoters, cellulose production was reduced in parallel with decreased cellulose synthase activity. These observations suggest that the expression of the bcs operon is rate-limiting for cellulose synthesis in A. xylinum.