Hirata H, Negoro S, Okada H
J Bacteriol. 1984 Oct;160(1):9-14. doi: 10.1128/jb.160.1.9-14.1984.
Bacillus stearothermophilus IAM11001 produced three beta-galactosidases, beta-galactosidase I, II, and III (beta-gal I, II, and III), which are detectable by polyacrylamide (nondenatured) gel electrophoresis. By connecting restriction fragments of the chromosomal DNA to plasmid vectors, followed by transformation of Escherichia coli, two beta-galactosidase genes (bgaA and bgaB) located close to each other on the chromosome were isolated. Identification of the gene products and Southern hybridization analyses with a 2.7-kilobase-pair EcoRI fragment containing the bgaA gene as probe revealed that a single bgaA gene exists on the genome and that beta-gal II and beta-gal III consist of a common subunit (the bgaA gene product; molecular weight, 120,000), but differ in their assembly (beta-gal II is a dimer, and beta-gal III is a tetramer). The bgaB gene product (molecular weight, 70,000) in Bacillus subtilis harboring pHG5 (a hybrid plasmid consisting of pUB110 and a 2.9-kilobase-pair EcoRI fragment) was estimated to be the beta-gal I protein from its heat stability. Southern hybridization and immunological testing indicated that the two genes have no homology.
嗜热脂肪芽孢杆菌IAM11001产生三种β-半乳糖苷酶，即β-半乳糖苷酶I、II和III（β-gal I、II和III），通过聚丙烯酰胺（非变性）凝胶电泳可检测到它们。通过将染色体DNA的限制性片段连接到质粒载体上，随后转化大肠杆菌，分离出了染色体上彼此相邻的两个β-半乳糖苷酶基因（bgaA和bgaB）。用包含bgaA基因的2.7千碱基对EcoRI片段作为探针进行基因产物鉴定和Southern杂交分析，结果表明基因组上存在单个bgaA基因，β-gal II和β-gal III由一个共同的亚基（bgaA基因产物；分子量为120,000）组成，但它们的组装方式不同（β-gal II是二聚体，β-gal III是四聚体）。携带pHG5（一种由pUB110和一个2.9千碱基对EcoRI片段组成的杂交质粒）的枯草芽孢杆菌中的bgaB基因产物（分子量为70,000），从其热稳定性推测为β-gal I蛋白。Southern杂交和免疫检测表明这两个基因没有同源性。
